Fig. 1.—Showing melted emulsion in coater ready for coating.
Fig. 1.—Showing melted emulsion in coater ready for coating.
Two or three years ago, when it was the practice to warm the plates before coating, I found from a series of experiments I then made that when a plate was warmed before being coated the emulsion commenced setting on the surface of the film, and of course in setting contracted, thereby leaving a partial vacuum between the film and the glass. On development frilling was the consequence. I found, however, that, when pouring the same emulsion on cold glass, on the portion of the plate where it was poured on, the film instantly chilled and commenced to contract on to the glass, and it never frilled there; but toward the edges of the plate, as the emulsion had commenced to chill before they were covered, the film was not in such perfect contact with the glass. Any person can try the experiment by first coating a plate in the ordinary way, and on the second plate just pour a small pool of emulsion on the center; let both dry, and he will then see after exposure which frills the easier on development.
Fig. 2.—Showing emulsion flowing through the slit on to the glass.
Fig. 2.—Showing emulsion flowing through the slit on to the glass.
After a series of experiments I found that by brushing a substratum of emulsion on to the cold plate (with a brush made by binding a strip of wash-leather at the end of a strip of glass), and then pouring the full quantity of emulsion on to the substratum (for quarter-plates I used a small silver teaspoon, which held sufficient to cover that size of plate), I found I could coat plates far better and quicker and as easily as when coating with collodion, and I got over the difficulties of having frilling plates.
When only a few small plates are required—such as for experimental purposes—I believe this method is as quick and good as any; but when several dozen plates are wanted, any plan of coating them separately takes a long time. With my plate-coater I can coat a dozen plates in about the time I formerly took to coat one. When coating a number, I thought it would be best to lay them in rows on the leveling-shelves and draw the receptacle containing the emulsion over them, rather than keep the latter a fixture and run the plates under it either on an endless band or sliding shelves; because by the first mode the plates can be fixed close together, and the emulsion is less likely to get between them.
The coater is a species of wooden tray (of which the diagrams show the section), having a small slit in one of the bottom edges through which the emulsion passes in one even wave the whole width of the plate. The width of the coater is the same as that of the plate, though one six and a half inches wide can be used for either half or whole plates.
Fig. 3.
Fig. 3.
I find the best way of making it, so as to get the slit an equal opening the whole length of it, is to put the back, bottom, and two sides together first, as in Fig. 3. Then by putting a piece of very thin paper (A B) on the angle piece when the front piece of wood is put tight down on the paper and fixed in its place, and the paper is drawn out, it will be found that the slit is very even. In one coater I made I had the slit a little too wide an opening, and to reduce it I glued a piece of muslin over it. This I found was a great improvement, as it not only acted as a strainer, but it checked and caused a more even flow of the emulsion over the plate. I varnished the wood and muslin (except over the slit) with black Japan.
To coat the plates I put them close together in rows on the leveling-shelf, as shown below:
Fig. 4.
Fig. 4.
A is a thin, narrow ledge of wood. B B B are thin pieces of wood, in the center of each of which is a small slot and thumb-screw. The plates are pressed against A by the pieces of wood, B, and the thumb-screws are then fastened. The plates are thus kept from slipping about. All this, of course, can be done in ordinary white light. The light is then made non-actinic; the melted emulsion is poured into the reservoir of the coater, which is put to the left hand edge of the outer row of plates. It is then lifted up on edge, as in Fig. 2, and drawn slowly over the row of plates, and so on until the whole of the rows are coated. Of course when not coating plates it is kept in a horizontal position, as in Fig 1. The emulsion on the plates is allowed to set without being disturbed; the shelf is then slipped into the drying-box until the plates are dry, so that they are not touched from the time they are coated until they are dry and ready for packing.
I am at present engaged in making a modification of this coater to hold a much larger quantity of emulsion at one time, when a large number of plates require to be coated. It is something the shape of a flat teapot.
Fig. 5.—A A is a piece of curved glass. B a piece of coarse ground flat glass, ground side uppermost, sliding in two grooves in the wooden side. C is the handle fixed to the wooden back.
Fig. 5.—A A is a piece of curved glass. B a piece of coarse ground flat glass, ground side uppermost, sliding in two grooves in the wooden side. C is the handle fixed to the wooden back.
A piece of thin paper is placed on the curved glass, and the ground glass pushed close up and fixed by two small wedges, D. The paper is then slipped out, leaving a narrow, even opening between the two glasses. The width of this opening can be varied by using thicker paper if the plates require to be coated with a thicker film. By using this form the coater can be more easily cleaned, as the ground glass can be slipped right out at the back, and probably in passing from the opening to the plates over the curved glass the wave of the emulsion will be equalized as well as when passing through the muslin.
In a recent paper in theWochenblatt, says thePhotographic News, this investigator relates his experience of gelatine emulsion containing chloride and iodide of silver. Gelatine films containing pure chloride of silver can only be used in the camera in exceptional cases; if, however, iodide be added, the resulting iodo-chloride films answer most of the purposes of a gelatino-bromide plate. It may be remarked that with gelatino-chloride emulsion an image is easily developed with pyro or oxalate; but unfortunately, fogging is very liable to set in. On strongly diluting the developing solution and adding a large proportion of bromide, it is possible to obtain a clear deposit, but the image is so thin that it is quite useless for practical purposes.
Gelatino-iodide films possess totally different properties. The development is extremely slow, without any tendency to fog; thus the addition of a restrainer should be avoided. Iodo-chloride emulsion can be prepared either by dissolving the chloride and iodide salts in the gelatine solution, and then adding by degrees the silver nitrate; or by making two separate emulsions of chloride and iodide of silver, and then mixing the two after the washing process. It should be noted that the properties of a compound or a mixture of the two haloids are very different. A negative of the spectrum impressed on an iodo-chloride film, prepared by mixing the two emulsions, shows two colored deposits. The red end of the spectrum as far as the G line is reproduced in the negative as a red tone, while that part of the spectrum from G extending to the violet appears as a grayish violet deposit. When using Stolze's potash developer, the difference of the two tones on the negative appears even more marked.
Experiments were instituted to determine the most suitable proportion of the silver haloids to be suspended in the emulsion. For this purpose three emulsions were prepared according to the following formulæ:
No. 1.—Iodo-chloride Emulsion.
No. 2.—Same as No. 1. but with 0.15 potassium iodide instead of 0.05; and 1.65 silver nitrate instead of 1.55.
No. 3.—Same as No. 1, but with 0.64 potassium iodide instead of 0.05; and 2.14 silver nitrate instead of 1.55.
To prepare the emulsion, A and B were heated in a water bath and then mixed slowly, with thorough shaking. The mixture, after an hour's cooking, was allowed to stand over night; the emulsion was next washed for seventy-two hours, and after slightly diluting, at once poured over the plates. The emulsions prepared according to formulæ 1 and 2 transmit blue light, which, however, is much brighter than that exhibited by gelatino-bromide emulsion. No. 3 emulsion transmits an orange light.
Previous to cooking the emulsion, a small quantity from each sample was spread on a glass plate, and, with the films prepared from the fully digested emulsion, were placed in sunlight. The unripe emulsion darkened much more quickly than that which had been digested. The colors of the exposed films prepared according to Nos. 1 and 2 were chocolate, and there was very little difference between the tones of the ripe and unripe emulsion. With the plates made by No. 3 formula there was, however, a great difference of color noticeable; thus, while the unripe emulsion yielded a deposit not unlike that of Nos. 1 and 2, the films prepared from the ripe emulsion assumed a grayish green color, which did not alter even after some weeks' exposure to daylight.
Messrs.A. Boake & Co., of Stratford, London, England, have devised a convenient apparatus for charging water with sulphurous acid which is useful in the making of photographic developers. The following description has been furnished by the firm:
The figure shows one of the siphons connected with a very convenient form of apparatus for preparing a solution of sulphurous acid in water, or of sulphites, as may be required.
The siphons are easy to manage, the flow of gaseous acid being regulated with the greatest nicety by simply turning the milled head shown in the engraving, the liquid acid being gradually converted into gas as the pressure is relieved. There is, moreover, no danger attending the use of this simple apparatus; sulphurous acid exerting at ordinary temperatures a pressure of about 30 pounds on the square inch, while each siphon is carefully tested under a pressure of 200 pounds on the square inch before being sent out.
APPARATUS FOR SATURATING WATER WITH SULPHUROUS ACID.
APPARATUS FOR SATURATING WATER WITH SULPHUROUS ACID.
In preparing a solution, say, of sulphurous acid in water, the ground stopper carrying the tubes for passing the gas should be removed from the glass jar in immediate connection with the siphon, and two-thirds filled with distilled water; the stopper is then to be replaced, and the second glass jar half filled with caustic soda solution. The soda solution is used to absorb any sulphurous acid not dissolved by the distilled water, and so prevent the escape of this irritating gas into the air. Solution of sulphite of soda, and also of bisulphite, can be prepared in a similar way, substituting only pure caustic soda solution for the distilled water employed in the case of preparing the solution of sulphurous acid; but we must rather devise the purchase of the pure solid forms of these salts specially prepared, and put up by us in one-pound stoppered bottles for use in photography; these preparations can be obtained either direct from the manufacturers or from any wholesale chemical firm. The siphons may be obtained either separately or already connected with the absorbing jars. It may be mentioned that these siphons contain about two and a half pounds of liquefied sulphurous acid, and can be refilled when required; but those requiring larger quantities can obtain the acid compound in copper drums.
The Photographic Newssays: It will be noticed thatMessrs.Boake say there is no danger attending the use of the siphons, as the glass vessels are tested at a much greater pressure than that ordinarily exerted by the condensed sulphurous acid; but our readers must remember that a blow against a hard substance may cause the glass to become fractured, and that under these circumstances the bursting of a siphon might cause a serious injury. Still, if proper care is exercised, there need be no accident; but we would suggest that the condensed acid should always be kept in the coolest place available, as the pressure it exerts becomes much greater when the temperature is raised.
The above caution is necessary, as a bare statement that there is no danger may cause persons to handle the siphons without reasonable care. The risk is precisely analogous to that attending the use and handling of bottles containing ordinary aerated waters, only the irritating nature of the sulphurous acid must be taken into account. Instances have occurred in which serious injury has resulted from the bursting of a bottle of soda water; but few, if any, are deterred from the use of soda water or lemonade on this account.
The precipitation of tannin by a solution of gelatin is effected more completely and in a better condition for filtration if, besides ammonium chloride, as proposed by Schulze and Lehmann, there is also added a small quantity of chromium sulphate or of chrome-alum. The author proceeds in the same manner as Lehmann, but he adds to 100 c.c. of the solution containing sal-ammoniac from 5 to 8 drops of a solution containing 1 part chromium sulphate in 25 parts of water. In order to ascertain the end of the reaction, he filters small quantities into two test glasses of equal width, adds to the one a few drops of a solution of gelatin, observing if the two liquids, when held up against a sheet of black glazed paper, appear opaque or transparent. As long as a precipitate is formed, these portions and the washings of the little filters are poured back to the main quantity. If acetic or tartaric acid is present, the liquid should be neutralized before proceeding to the determination. Johanson points out that, though this method gives good results with the tannin of galls and of oak-bark, an extract of coffee gives no precipitate with solution of gelatin, so that caffeo-tannic acid cannot be determined in this manner. This shows that only quantities of tannin of one and the same kind can be compared with each other.
[Abstract of a paper read before the Chemistry Section of the British Association at Montreal.]
The author gave aresumeof the work he had done in continuation of the researches of Bunsen, E. von Meyer, Horstmann, and other chemists, on the division of oxygen when exploded with excess of hydrogen and carbonic oxide. The following are the general conclusions arrived at:
1. No alterationper saltumoccurs in the ratio of the products of combustion. The experiments made completely confirm Horstmann's conclusion; Bunsen's earlier experiments being vitiated by the presence of aqueous vapor in the eudiometer.
2. A dry mixture of carbonic oxide and oxygen does not explode when an electric spark is passed through it. The union of carbonic oxide is effected indirectly by steam. A mere trace of steam renders the admixture of carbonic oxide and oxygen explosive. The steam undergoes a series of alternate reductions and oxidations, acting as a "carrier of oxygen" to the carbonic oxide. With a very small quantity of steam the oxidation of carbonic oxide takes place slowly; as the quantity of steam is increased, the rapidity of explosion increases.
3. When a mixture of dry carbonic oxide and hydrogen is exploded with a quantity of oxygen insufficient for complete combustion, the ratio of the carbonic acid to the steam formed depends upon the shape of the vessel and the pressure under which the gases are fired. By continually increasing the initial pressure, a point is reached where no further increase in the pressure affects the products of the reaction. At and above this critical pressure the result was found to be independent of the length of the column of gases exploded. The larger the quantity of oxygen used, the lower the "critical pressure" was found to be.
4. When dry mixtures of carbonic oxide and hydrogen in varying proportions are exploded above their critical pressures with oxygen insufficient for complete combustion, an equilibrium is established between two opposite chemical changes represented by the equations:
(I.) CO + H2O = CO2+ H2.(II.) CO2+ H2= CO + H2O.
At the end of the reaction the product of the carbonic oxide and steam molecules is equal to the product of the carbonic acid and hydrogen molecules multiplied by a coefficient of affinity. This result agrees with Horstmann's conclusion. But Hortsmann considers that the coefficient varies with the relative mass of oxygen taken.
5. A small difference in the initial temperature at which the gases are fired makes a considerable difference in the products of the reaction. This difference is due to the condensation of steam by the sides of the vessel during the explosion, and its consequent removal from the sphere of action during the chemical change. When the gases are exploded at an initial temperature sufficiently high to prevent any condensation of steam during the progress of the reaction, the coefficient of affinity is found to be constant whatever the quantity of oxygen used—provided only the quantity of hydrogen is more than double the quantity of oxygen.
6. The presence of an inert gas, such as nitrogen, by diminishing the intensity of the reaction, favors the formation of carbonic acid in preference to steam. When the hydrogen taken is less than double the oxygen, the excess of oxygen cannot react with any of the three other gases present—carbonic oxide, carbonic acid, and steam—but has to wait until an equal volume of steam is reduced to hydrogen by the carbonic oxide. The excess of inert oxygen has the same effect as inert nitrogen in favoring the formation of carbonic acid. The variations in the coefficient of affinity found by Hortsmann with different quantities of oxygen are due partly to this cause, but chiefly to the varying amounts of steam condensed by the cold eudiometer during the reaction taking place in different experiments.
7. As a general result of these experiments it is shown that, when a mixture of dry carbonic oxide and hydrogen isexploded with oxygen insufficient for complete combustion, at a temperature at which no condensation of steam can take place during the reaction, and at a temperature greater than the critical pressure, an equilibrium between two opposite chemical changes is established, which is independent of the mass of oxygen taken, so long as this quantity is less than half the hydrogen. Within these limits the law of mass is completely verified for the gaseous system composed of carbonic oxide, carbonic acid, hydrogen, and steam at a high temperature.
At the July meeting of the Odontological Society of France,Dr.Cludius, from Grenoble, made the following demonstration of a new method of gold filling, saying:
We feel the necessity of making the operation of filling teeth with gold easier, if possible, especially in difficult cases, in order to lessen the fatigue of the operator, as well as to prevent the suffering of the patient, during hours without interruption, under the ceaseless blows of the mallet. The remedy has been sought in new forms of material, like sponge and crystal gold. These have not given any help in the performance of good operations, but have rather facilitated poor work. We are not in need of varieties in the forms of gold, but we ought to try and improve its manipulation, and this has recently been done in a novel manner byDr.Herbst, whose rotation method has been mentioned in the dental journals within only a few months; and yet it seemed necessary that this great invention, made in Bremen, should take its way by America to come to us.
In the January meeting of the Odontological Society of New York,Dr.Bödecker mentioned it for the first time, describing the excellence of fillings made byDr.Herbst in less than half the time that any mallet work would have required, and he expressed his intention of going to study the method with the inventor. Thinking that I was yet nearer to Bremen, I went thither, and found thereDr.W. D. Miller, who had come on the same errand. Mr. Brasseur had also written toDr.Herbst, and it is by his (Mr. B.'s) invitation that I came to Paris to show you what I have learned in Bremen. To-morrow morning I shall show the method in the mouths of patients at the Dental College of France.Dr.Herbst did not patent his new method, to which may be given the name of "rotation gold filling." All he desires is that every one may try the system, and he feels himself already largely paid by the acknowledgments he is daily receiving.
He proves that by his way of rotation one is able to adapt the gold more perfectly to the walls of the cavity than by any other means hitherto employed. One can thus work gold in the very weakest teeth, because there is no force employed, yet the gold is as much condensed as by any mallet known.
The new instruments are very simple, and you may find them in the dental depots. One can easily prepare them for himself—at least the principal one, No. 5—by putting a broken burr in the hand-piece and holding it like a pen for writing until the rotating end of the burr is ground to a roof-like shape, on a dry Arkansas stone. Nos. 1, 2, 3, and 4 are smooth burnishers, and help to fix the first layers of gold in large fillings. They are afterward used as finishers, Nos. 9 to 17 are finishing burnishers, and No. 18 is a needle-point finisher.
The cavity is to be prepared in the usual way, but retaining points are very much less needed than for other methods. Take, for instance, a central cavity in a molar—and, moreover, the fundamental idea of this system is to transform all cavities to be filled into central cavities. Now fix several cylinders, of a size proportioned to the cavity, with a common plugger, and then take No. 2, or 3, or 4, and by a slow rotation polish the gold against the walls. If the gold does not stick directly, put in more cylinders with the plugger, and recommence the condensation with the burnisher. On this first layer of gold a second one is to be made to adhere; but the polished surface prevents, and here No. 5 finds employment in quick rotation and interrupted touches until the polish is gone. (I may here remark that the gold is condensed by this rotation and without pressure in a very remarkable way.) For large fillings, No. 5 is to have proportionate points,13which, if too fine, will make holes in the gold, and the pressure is to be intermittent, in order to avoid the development of heat, which would be painful and irritating to the pulp.
All the instruments by use get gilded, and will not work longer without tearing out the gold; but this inconvenience may be prevented by occasionally rubbing them while in rotation upon a piece of tin.
The filling of the cavity is continued in the way above described.
Let us now take the case of two incisors with lateral cavities approximating one another. The two cavities, prepared as usual, are treated as if one, and the gold is at the same time introduced into both cavities, fixing some cylinders in the four corners by rotation of the proper burnishers, and condensation with No. 5, until they are filled, so that there appears to be a single mass of gold. No. 18 is then pushed with regular rotation between the teeth until the mass is quite separated, so that thin files, and disks, and tapes may be employed in finishing the fillings.
In filling similar cavities between the second bicuspid and first molar, after they are properly prepared, place a matrix and fill one cavity with shellac to retain the matrix, and distribute the resistance, and then fill the other like a central cavity, beginning at the cervical border, and pressing especially against the matrix at that point, work toward and finish at the middle of the crown. Having filled the first one, remove the shellac and fill the other in the same way.
The rotation and the pressure,if intermittent, do not produce heat—at least, not more than will render the gold cohesive.
Dr.Herbst filled for me two molars, carious to the cervical border, and very sensitive there, for which reason they had for years been filled with plastics, because I was afraid of perforation if retaining points were made, without which gold filling by malleting would not have been possible; and I was too nervous to sit three or four hours in the chair.Dr.Herbst filled both teeth by rotation, without retaining points, in a little more than one hour. Several gentlemen present have seen them and observed the severe tests to which Mr. Brasseur subjected them, and I may add that notwithstanding the great sensitiveness of the dentine and the proximity of the pulps, I felt not the least inconvenience from heat, and my own patients bear like testimony.
We will now split a crown filled in the hand, and you see that the gold is pressed into the smallest depressions of the interior surface, and is so uniformly condensed as to resemble an ingot, impossible to separate in pieces, yet you may note the different stages of the rotation.
I sawDr.Herbst fill six cavities—some of them large ones—in front teeth, taking altogether at the same sitting about one hour.
It would be difficult to precisely describe the manipulation requisite for the great variety of cases presenting in practice, but I have explained to you in theory the typical ones in the hope of stimulating you to try this method of filling by rotation, which I look upon as one of the most ingenious modes yet given to our profession. The results are splendid, and the operator will thereby save much time and prevent great suffering on the part of the patient.
An important conference upon cholera was held in Berlin, at the Imperial Board of Health, on the evening of July 26. There were presentDrs.Von Bergman, Coler, Eulenberg, B. Frankel, Gaffky, Hirsch, Koch, Leyden, S. Neumann, Pistor, Schubert, Skrezcka, Struck, Virchow, and Wollfhugel. The conference had been called at the instance of the Berlin Medical Society, whose President, Professor Virchow, explained that it was thought advisableDr.Koch should in the first instance give a demonstration of his work before a smaller body than the whole Society, so that the proceedings might be fully reported in the medical press. He mentioned that Herr Director Lucanus and President Sydow had expressed their regret at being unable to be present, as well as many others, includingDrs.Von Lauer, Von Frerichs, Mehlhausen, and Kersandt.Dr.Koch first showed various specimens of the bacilli and their method of preparation (seeBerliner Klinische Wochenschrift, August 4). This resembles that for the tubercle bacillus, viz., drying on a cover glass and staining with fuchsin or methyl-olin. Koch then gave a history of his work while in Egypt and India. His post-mortem examinations led him to believe that the intestines were the nidus of the disease. At first his microscopical examinations were unsatisfactory, but finally he got fresh dejecta and acute cases, and then discovered the comma bacillus.
This, he said, is smaller than the tubercle bacillus, being only about half or at most two-thirds the size of the latter, but much more plump, thicker, and slightly curved. As a rule, the curve is no more than that of a comma (,), but sometimes it assumes a semicircular shape, and he has seen it forming a double curve like an S; these two variations from the normal being suggestive of the junction of two individual bacilli. In cultures there always appears a remarkably free development of comma-shaped bacilli.
These bacilli often grow out to form long threads, not in the manner of anthrax bacilli, nor with a simple undulating form, but assuming the shape of delicate long spirals—a corkscrew shape—reminding one very forcibly of the spirochæte of relapsing fever. Indeed, it would be difficult to distinguish the two if placed side by side. On account of this developmental change, he doubted if the cholera organism should be ranked with bacilli; it is rather a transitional form between the bacillus and the spirillum. Possibly it is true spirillum, portions of which appear in the comma shape, much as in other spirilla,e. g., spirilla undula, which do not always form complete spirals, but consist only of more or less curved rods. The comma bacilli thrive well in meat infusion, growing in it with great rapidity. By examining microscopically a drop of this broth culture the bacilli are seen in active movement, swarming at the margins of the drop, interspersed with the spiral threads, which are also apparently mobile. They grow also in other fluids,e. g., very abundantly in milk, without coagulating it or changing its appearance. Also in blood serum they grow very richly. Another good nutrient medium is gelatine, wherein the comma bacilli form colonies of a perfectly characteristic kind, different from those of any other form of bacteria. The colony when very young appears as a pale and small spot, not completely spherical as other bacterial colonies in gelatine are wont to be, but with a more or less irregular, protruding, or jagged contour. It also very soon takes on a somewhat granular appearance. As the colony increases the granular character becomes more marked, until it seems to be made up of highly refractile granules, like a mass of particles of glass. In its further growth the gelatine is liquefied in the vicinity of the colony, which at the same time sinks down deeper into the gelatine mass, and makes a small thread-like excavation in the gelatine, in the center of which the colony appears as a small white point. This again is peculiar; it is never seen, at least so marked, with any other bacterium. And a similar appearance is produced when gelatine is inoculated with a pure culture of this bacillus, the gelatine liquefying at the seat of inoculation, and the small colony continually enlarging; but above it there occurs the excavated spot, like a bubble of air floating over the bacillary colony. It gives the impression that the bacillus growth not only liquefies the gelatine, but causes a rapid evaporation of the fluid so formed. Many bacteria also have the power of so liquefying gelatine with which they are inoculated, but never do they produce such an excavation with the bladder like cavity on the surface. Another peculiarity was the slowness with which the gelatine liquefied, and the narrow limits of this liquefaction in the case of a gelatine disk. Cultures of the comma bacillus were also made in agar-agar jelly, which is not liquefied by them. On potato these bacilli grow like those of glanders, forming a grayish-brown layer on the surface. The comma bacilli thrive best at temperatures between 30° and 40° C., but they are not very sensitive to low temperatures, their growth not being prevented until 17° or 16° C. is reached. In this respect they agree with anthrax bacilli. Koch made an experiment to ascertain whether a very low temperature not merely checked development, but killed them, and subjected the comma bacilli to a temperature of -10° C. They were then completely frozen, but yet retained vitality, growing in gelatine afterward. Other experiments, by excluding air from the gelatine cultures, or placing them under an exhausted bell-jar, or in an atmosphere of carbonic acid, went to prove that they required air and oxygen for their growth; but the deprivation did not kill them, since on removing them from these conditions they again began to grow. The growth of these bacilli is exceptionally rapid, quickly attaining its height, and after a brief stationary period as quickly terminating. The dying bacilli lose their shape, sometimes appearing shriveled, sometimes swollen, and then staining very slightly or not at all. The special features of their vegetation are best seen when substances which also contain other forms of bacteria are taken,e. g., the intestinal contents or choleraic evacuations mixed with moistened earth or linen and kept damp.
A most important statement was that the comma bacillus seems to be killed by the bacteria of putrefaction, and consequently agents that destroy the latter organisms without the former may really do injury, by removing from the cholera bacillus an impediment to its growth.
As for destructive agents to the bacillus, he found it killed by solutions in the following proportions: oil of peppermint, 1 in 2,000; sulphate of copper, 1 in 2,500 (a remedy much employed, but how much would really be needed merely to hinder the growth of the bacilli in the intestine!); quinine, 1 in 5,000; and sublimate, 1 in 100,000.
In contrast with the foregoing measure for preventing the growth of these bacilli is the striking fact that they are readily killed by drying. This fact is proved by merely drying a small drop of material containing the bacilli on a cover glass, and then placing this over some of the fluid on a glass slide. With anthrax bacilli vitality is retained for nearly a week; whereas, the comma bacillus appears to be killed in a very short time.
Dr.Koch having found and cultivated the comma bacillus and ascertained its distinctive character, next proceeded to investigate its relation to cholera. In all there were now about one hundred cases of cholera in which the bacillus had been found, while it was never found in connection with other diseases. Three different views, said the speaker, as to its relation to the cholera process are tenable:
1. That the disease favors the growth of these bacilli by affording them a suitable soil. If so, it would mean that the bacillus in question is most widely diffused, since it has been found in such different regions as Egypt, India, and France; whereas the contrary is the case, for the bacilli do not occur in other diseases, nor in the healthy, nor apart from human beings in localities most favorable to bacterial life. They only appear with the cholera.
2. It might be said that cholera produces conditions leading to a change in form and properties of the numerous intestinal bacteria, a pure hypothesis; the only instance of such a conversion refers to a change of physiological and pathogenic action, and not of form. Anthrax bacilli under certain conditions lose their pathogenic power, but undergo no change in shape; and that is an instance of a loss of pathogenic properties, while there is no analogy to support the view of the harmless intestinal bacteria becoming the deadly cholera bacilli. The more bacterial morphology is studied, the more certain it is that bacteria are constant in their form; moreover, the comma bacillus retains its special characters unchanged through many generations of culture.
3. Lastly, there is the view that the cholera process and the comma bacilli are intimately related, and there is no other conceivable relation but that the bacilli precede the disease and excite it. "For my own part," saidDr.Koch, "the matter is proved that the comma bacilli are the cause of cholera."
Dr.Koch then described his attempts to inoculate lower animals with the bacillus, and explained the cause of his failure in the natural immunity of the animals against the disease.
In advocating the local Indian origin of the disease he said: That the virus can be reproduced and multiplied outside the body is apparent, since the bacillus can be cultivated artificially, and its growth is not affected by comparatively low temperatures. Probably it does not grow in streams and rivers, where, owing to the current, a sufficient concentration of nutrient substance does not occur; but in stagnant water and at the mouths of drains, etc., vegetable and animal refuse may accumulate and afford the necessary nutriment. Thus is explained the propagation of cholera by the subsoil water, and the increase of epidemics with the sinking of its level, which lessens the flow and diminishes the amount of surface water. Admitting the dependence of cholera upon this micro-organism it is impossible to conceive the disease having an autochthonous origin in any particular place; for a bacillus must obey the laws of vegetable life, and have an antecedent; and since the comma bacillus does not belong to the widely diffused micro-organisms, it must have a limited habitat. Therefore, the occurrence of cholera on the delta of the Nile does not depend on its resemblance to the delta of the Ganges; but the disease must have been imported there as it is into Europe. It was once thought that an outbreak in Poland had a local origin until it was discovered to have been introduced from Russia. Again, about ten years ago, there was a sudden outbreak at Hamar (Syria), thought to be an instance of local origin, but erroneously, as shown by a statement of Lortet, who told Koch, when at Lyons, that the epidemic had been introduced into Hamar, where he was at the time, by Turkish soldiers from Djeddah. All great epidemics of cholera began in South Bengal, where the conditions for the development and growth of the bacillus are most perfect.—Med.Record.
The notes of a few cases of the use of the hydrochlorate of cocaine will illustrate its perfect efficiency in some and its apparent inertness in others, and may help toward its proper application and general appreciation.
In a double extraction of hard cataract there was no pain produced by the graspings of the conjunctiva in the fixation of the eyes, in the corneal incisions, and in the iridectomies.
A 4 per centum solution was freely brushed over the entire conjunctival surface three times, at intervals of ten minutes, and the operations were commenced in forty minutes after the first application. No irritation was produced, and the only sensation described was that of "numbness and hardness." The entire conjunctival surface seemed insensible to repeated pinching with the fixation forceps.
In a single extraction of hard cataract a 4 per centum solution was brushed over the ocular and palpebral conjunctiva, with the eyelids freely everted. Three applicationswere made at intervals of ten minutes, and the operation was performed at the lapse of twenty-five minutes. The patient asserted decidedly that she felt no pain whatever.
Preparatory to the operation for uterine procidentia and rectocele, the vaginal and labial mucous surface was wiped dry, and a 4 per centum solution of the hydrochlorate of cocaine was thoroughly brushed over it. The sensitiveness was tested at three intervals of ten minutes each, and the application was repeated three times. There appeared to be at no time any decided loss of painful sensibility, and the operation was finally performed under the anæsthesia of sulphuric ether.
For the removal of a rather large tarsal tumor, the ocular and palpebral conjunctiva and the exterior of the eyelids were brushed with the solution as previously used, at intervals of ten minutes, and the excision was performed at the lapse of forty minutes. The operation seemed to be as painful to the patient as if performed without an attempt at anæsthesia.
For the operation for lachrymal obstruction the application was made in the same manner and at the same intervals. The slitting of the punctum and caniculus gave no pain, but the passage of the dilating probe down the lachrymal canal seemed to produce some uneasiness.
Prior to applying nitric acid as a caustic to a syphilitic ulcer on the tongue, the same manner and number of applications were repeated, the tongue having been wiped dry and held protruding between the teeth. No pain was produced on the thoroughly benumbed tongue.—Med.News.
The outcome of several public inquiries which have taken place during the last year or two, and of much valuable data derivable from other sources, establishes, we think, a well marked advance with reference to sewage disposal; and it may be of use, as well as of interest, if we lay before this Congress the conclusions which, we conceive, are deducible therefrom. We propose to deal with the subject under the following heads: 1. Sewage disposal on land. 2. Sewage disposal by chemical treatment. 3. Sewage disposal by discharge into a tidal river, or into the sea, without treatment.
The object of dealing with sewage on land may be taken as twofold, namely, to purify it (which is the sanitary object), and to utilize its manurial products (which is the agricultural object). Where want of skill or where prejudice has existed, these two have not been properly separated, and the results have been in many cases unfavorable to sewage disposal on land from either of the before mentioned points of view. It has been regarded as an axiom that clay land cannot be employed to clarify sewage. This is true when it is proposed to pour the sewage on it as if the land were porous. Very recent experience, however, has led to clay land being converted from an impervious to a pervious condition, by which it has been successfully utilized. This is effected by digging out the clay to a depth of about 6 ft., burning it into ballast and replacing it in layers interposed with an occasional layer of open alluvial soil, the whole area being well drained with a free outlet for the effluent. We have successfully carried this plan out, and with this result, that whereas it was not possible previously to clarify the sewage of 100 people to an acre of clay land, the prepared filtration area has been able to continuously clarify the sewage of about 1,500 people to the acre. The cost of converting clay land into this form of filter may be taken as varying from £750 per acre to £1,000 per acre, according to local circumstances. One area which we have just completed has cost £1,000 per acre. Before sewage is passed on to these filters (or on to land) it should be strained so as to remove the larger particles. The best arrangement for this purpose is to pass the sewage upward through a straining medium (not downward), and to run the solids from the bottom of the straining tank on to a low lying piece of land for digging in as they are run out. Where such a filtration area is made to form part of a sewage farm it acts as a safety valve, and enables the land and crops to have a rest when they do not require further irrigation; at the same time the process of purification is not interrupted. If open, porous land is available for sewage purification, and if it can be drained 6 ft. deep to a good free subsoil, so that the effluent can get readily away, we find that the sewage of from 600 to 700 people can be dealt with on each acre per annum with both good agricultural and sanitary results.
In our address as President of the Engineering and Architectural Section of the Congress of this Institute at Newcastle upon Tyne, in 1882, we directed attention to the important investigation which had been conducted by Mr. R. Warrington, of Rothamsted, the result of which was to show the action which goes on in the soil when sewage is passed through it. Further information which the same observer has published since that date is of equal value, and deserves to be read by all who have to advise in regard to sewage disposal on land. The process of "nitrification" (as it is termed), which he has so fully investigated, consists in the conversion into nitrates (which serve to nourish plant life) of the organic matter in sewage. This takes place by the action of a living ferment of the bacteria family, which is created by and feeds on the impurities in sewage, and these organisms both consume the impurities and convert them into nitrates. The action of living agents thus brings about the oxidation of the organic matter in sewage, just as worms, larvæ, fungi, and insects feed on the vegetable matter in the soil, increasing the amount of nitrogenous material in it. Experience during the past year or two has proved the feasibility of preserving green crops in a succulent state by compressing them in silos, so that they can be utilized for cattle fodder in the winter. This system deserves notice in connection with sewage farming, as we are of opinion that it will prove a valuable means of getting over the well known practical difficulty which is experienced of finding a market for the large amount of green crop which is produced by sewage irrigation. In speaking of this system the term "silo" is applied to the artificial chamber or receptacle for green crops (such as grass, vetches, clover, etc.).
The term "silage" is applied to the crop thus treated, and the term "ensilage" is applied to the process of making "silage." The details of the construction of silos cannot be referred to here, beyond stating that what is required is to construct a pit or chamber either in the form of an excavation in the ground, with a brick or other lining, or by building it above the ground. The object is to enable the green crop to be deposited in an air and water tight chamber, in which pressure can be applied to the crop to compress it. This is effected in some cases by well treading the crop after it is laid in the silo, and then spreading layers of earth to about a couple of feet, and pressing the covering well down. Another way is to construct the silo with a movable covering of the exact size and shape of its interior. This cover is raised and lowered by suitable chains and rollers. After the crop is placed in the silo, the cover is lowered and weighted so that a thorough compressing is effected; the weight applied giving about 200 lb. or so per square foot of surface. Salt is sometimes added as the crop is placed in the silo. A crop thus dealt with is stored for months; when the silo is opened the fodder is found preserved, and in a state readily taken to by cattle. It is desirable to choose the site for the silos so that the fodder is preserved somewhere near the place of consumption; also to lay out the works so that as little handling as possible is required. For instance, the silo should be on sidelong ground, so that the crop can be carted and tipped at a high level, and the silage taken out for use at a lower level.
In the last edition of our book on "Sewage Disposal," in speaking of precipitation we said that "the purification of sewage by chemicals has been the subject of misapprehension, owing to the extravagant advantages which have been claimed for the system by its advocates." This is even more true now than it was two years ago, inasmuch as in the recent scheme for dealing with the sewage of the Thames Valley chemical treatmentper sewas relied on to produce from the sewage of a future population of 350,000 an effluent at all times fit to be discharged at one point into the river Thames above London; but the Parliamentary Committee rejected it. One part of the report of this Committee deserves attention, when speaking of sewage treatment by chemicals. It is as follows: "Your committee believe that in these cases the process of filtering the chemically purified effluent through earth ought, if possible, to be adopted, which was not provided for in the scheme under their consideration." This opinion is exactly in accordance with our experience, and is that which we have held throughout. It is at the root of the whole matter, because efforts are made by those interested in chemical processes to attain as high a standard of purity as possible with the attendant heavy expense of chemicals. Experience shows that it is impossible at all times and seasons to be sure of a constant and uniformly high standard of purity, and that chemical works should be supplemented by a filtration area, however small. The addition of this, however, enables a lower standard of effluent from the precipitation tanks to be admissible, and this can be attained with very simple and inexpensive chemicals.
In the course of our practice we have had to advise as to the majority of the processes, and to design the works for their being carried into operation. We have found that the cost of such works complete varies from 0.091 to 0.166 pound per head of the population, and that the average cost of the works at several towns which we have been connected with is 0.123 pound per head. This figure may be conveniently followed by that of the cost of treatment, which we find varies from 0.036 to 0.110 pound per head per annum, and an average of several places gives 0.06 pound per head per annum. The above figures apply only to places where the very highest standard was sought to be attained, but our more recent experience leads us to modify the arrangement of the works and the cost of treatment, so as to rely on filtration of the effluent as an important factor. We estimate that under these conditions the cost of the works complete would be about 0.075 pound per head, and the cost of treatment 0.04 pound per head per annum. The disposal of the sludge has always been a difficulty in these works, but this is now overcome in two ways: either by digging it into the ground, as is done at Birmingham now, or by pressing it into cakes in filter presses. It is found at Birmingham that one ton of sludge with 90 per cent. of moisture is produced from 1,000 people. There the lime process is used. We have found that about one ton to 2,000 people is produced where a salt of alumina or iron is used with the lime. At Birmingham the sludge is dug into the land adjoining the works, and it is found that one square yard of land will take one ton of sludge with 90 per cent. of moisture once in three years, which results in three yards of land being required to be provided for each ton of sludge. This system of digging in sludge is successfully carried out as regards freedom from nuisance. Where land is not available to dig in the sludge, it is necessary to make it portable for removal and disposal away from where it is produced. This is best effected by filter presses. Appliances are made for this purpose, by which the sludge is pressed to a consistency of about 50 per cent. of moisture. The cost of effecting this is about 0.007 pound per head per annum. It is found in practice that where the sludge is produced by straining the solids from sewage before passing it on to land for purification, it requires a little lime to enable the press to work well. About two barrow loads of lime for each ton of pressed sludge suffices.
It has been thought that the cost of precipitation would be covered, and even a profit gained, by the sale of the sludge. This hope, however, is not nearer realization now than it was in the time, now gone past, when chemical processes were relied on to turn sewage from a profitless into a profitable commodity. There is, consequently, less justification now than there was at that time for adopting a precipitation system for sewage disposal. It is entirely a question of carefully considering the engineering and financial points involved, regardless of the sanguine representations of interested or enthusiastic advocates of any particular system. As the estimated manurial value of the sludge which is precipitated from sewage by the addition of chemicals does not seem to be capable of realization, we think that probably the reason may be found in the fact that the chemicals arrest that process of decomposition which is essential to the conversion of the organic matters into nitrates for vegetation to utilize.
This explanation will be understood in the light of what we have already described in regard to "nitrification." If this view is correct, it would follow that the more completely and permanently the sludge is deodorized by the chemicals, the less capable is it of passing through the necessary stages of decomposition by which its manurial value can be realized. As mistakes are constantly being made in regard to the weights of sludge with varying degrees of moisture, the following table may be useful:
We will next deal with the conditions which should be fulfilled where it is sought to utilize a river or the sea into which to cast the sewage of a town. If it can be ascertained beyond question that at the proposed point of discharge the currents at all times will carry the sewage right away, and will not at the same time produce mischief at a distance (which is often omitted from the consideration), then that arrangement may be accepted as a good one. This, however, seldom occurs.
A river has been looked upon by manufacturers and local authorities as the natural carrier of their refuse from their district. This view has been persevered in, in spite of the River Pollution Prevention Act of 1876, which is practically a dead letter. The public, however, who use a river either for pleasure purposes or for obtaining their water supply, have of late years grown more and more united in their efforts to stop this abuse; and there is no doubt that these efforts will eventually succeed. In a paper which we read last year at the Congress at Glasgow, we pointed out the steps that were necessary to be taken to render this act operative, and we refer our hearers to that paper if they wish to follow the matter further. The effect of discharging sewage matter into a river has been the subject of much controversy among chemists. Some allege most positively that the injurious properties in the sewage are indestructible. This has led to alarmists demanding that under no circumstances ought sewage to pass untreated into a river.
We have given considerable attention to this vexed question, as it requires to be grasped by any engineer who has to advise on the selection of sewer outfalls, and it appears to us that the balance of evidence is against the alarmists. Every river has a certain power of oxidizing impurities in proportion to the extent of oxidation of the river itself. Besides this, there are the powerful purifying influences exercised by the plants and animalcules which exist in rivers.
It has been ascertained that entomostraca consume dead animal matter; and where this is wanting they do not live, but where it is in abundance they thrive. It follows, then, these minute animals exercise an important function in absorbing sewage impurities. They multiply prodigiously in these impurities, and are both created by them and fed upon them, converting foul and dangerous matters into harmless ones, in a similar way to that which we have referred to as nitrification when speaking of the action of bacteria in the soil. Considering that these organisms arise from and are fed on concentrated filth, it is obvious that they cannot live when the conditions favorable to their existence disappear. This would be the case when the sewage is discharged into a large volume of water with a different temperature to that which suits them, and with powerful oxidizing influences at work. These conditions, added to the difficulty they must experience to find their natural food—namely, concentrated sewage—where the sewage matter becomes so greatly diluted, accounts for the fact that in a short run of a good river sewage impurities largely disappear. The action of weeds and plants also aids purification to a very large extent. Minute plants, such as confervoid algæ and the like, also assist in oxygenating the river, as when exposed to light they decompose carbonic acid, and liberate oxygen.
The practical question which has to be answered in every case where sewage is proposed to be discharged into a river requires to be approached from two points. The first is whether a nuisance will be caused at the spot to which objection would be taken. If this is likely to be the case, then the fact that the sewage will get purified in a short run of the river does not meet the objection. The second point requires a careful consideration of the condition of the river, both from an engineering as well as from a chemical and biological point of view. Decisions on these matters have too often been arrived at in a rough and ready way. They require skillful treatment, as the interests—both commercial and hygienic—which are affected are too great to permit of them being dealt with by any who are not well informed and careful. The general conclusions which we deduce from our observations are as follows:
1. That chemical precipitation is not so necessary now as it was considered to be a few years ago, in cases where land for irrigation is not procurable.
2. That the efforts to profitably remove the manurial elements from sewage by chemicals not having been successful, the system should be adoptedper seonly where a filtration area cannot be obtained.
3. That the success which has attended the construction of filtration areas where the land is clayey, and the successful results which have been obtained from a combined straining of sewage and of subsequent filtration through small areas of artificial filters, point to the adoption of one or other of these systems in many cases where chemical treatment would previously have been advised.
4. That the injurious effects of passing untreated sewage into a river depend upon not merely the relative volumes of the sewage and the river, but chiefly upon the power of the river to oxidize the sewage, which power is in proportion to the extent of oxidation of the river itself.
An article in the local news columns of theTribunesays:
The loud outcry made a few years ago against the old fashioned plush covered spring cushions, then used in street car for seats and backs, caused them to be removed and set car builders at work to make a car that would be light, healthy, and comfortable. The general plan of perforated wooden seats with plain backs has been adopted by all the companies. They are covered with a fine quality of heavy Axminster carpet during the winter, and in the summer nearly all the cars have only wooden seats and backs. Open cars are used on a number of routes during the summer, and this is conducive to the health of passengers. The only particular difference in the furniture of the cars is the mats used on the floor. Seven of the lines use sectional wooden mats of plain or ornamental design, while three retain cocoa mats. Wooden mats are the easiest to clean. Cocoa mats retain moisture on damp or rainy days, and emit a musty odor. There are four sets for each car, and they are changed every trip on rainy days.
The First and Second Avenue routes, under one management run 150 cars; the Third Avenue, 180; the Fourth, 75; the Sixth, 88; the Broadway and Seventh, 135; the Eighth and Ninth, 160; and the Tenth, 120. At the stables of each the same general arrangement for cleaning cars is used, while the details only are different, being regulated by the judgment and experience of superintendents. From six to fifteen men are employed for cleaning cars by the different companies.
After every round trip that a car makes, it is taken to the stable, the mats are taken off the floor, and two men withbrooms and specially constructed brushes give it a thorough sweeping and brushing. After a car makes its last trip at night, it is run upon what is termed the washstand, which is a large turn table surrounded by hydrants. Everything movable is taken out of it, and water is played from a hose on the inside and outside, while four men with scrubbing brushes and stiff brooms remove whatever dirt has accumulated during the day. After this operation the car is run upon a side track, and two men dry the inside and polish the windows.
While passengers find fault with the untidiness of street cars, superintendents have a word also of complaint against passengers. If men would not convert a car into a spittoon for the reception of cigar stumps, tobacco spit, and quids, and a garbage box for nut-shells, fruit rinds, cores, and pits, the remnants of lunches and old papers, it would be much easier to keep up a cleanly appearance. Section 167 of the Sanitary Code, which provides that no soiled article of clothing or bedding shall be carried on street cars, except on the front platform, is strictly enforced by all the companies, and it is worth a conductor's position if he is proved derelict in this respect.
Nearly all the car companies build their own cars, and all have repair shops at their stables, and as soon as a car is damaged by a collision it is sent at once to the shop and repaired. Men are detailed to keep a strict watch over all the working parts of cars.
No metal or plate has yet been found of which to make a hand railing that will keep bright and untarnished. Many experiments have been tried, but the hardest plate that can be obtained will not stand the friction of the hands longer than two months, before the plated metal will show through. Cars are painted and varnished at least once a year. The various parts of the car last different periods. The wheels average about eighteen months on long routes; on short routes, about two years. Steps and platforms last about five years. There is no particular limit for the floors and framework, as they are but little worn. Cars are frequently built up from an old floor or framework, but at the end of about fifteen years there is but little left of the original car.