FIG. 39.
The ears of degenerates frequently grow in later life to an enormous size. On examination of 207 paupers over 50 years old the shortest ear was found to be 2·25 inches, the longest 3·36; the average on the right side was 2·73, on the left 2·76; the narrowest ear was ·88, the widest 1·50, the average 1·26. These results, compared with the results of the measurements of normal persons from 12 to 50 years, plainly demonstrate that the ears of degenerates grow after the twenty-sixth year, when the skeleton has completed its development. With such large ears other stigmata are generally associated. A few of the best types of stigmata of the ear illustrate better than any description the general characteristics. Fig.39illustrates the earpar excellenceof degeneracy, the typical jug-handled ear first described by Morel and called by his name. This consists of a long, narrow ear attached its entire length, and tapering upward and outward from the lobe to the point where the Darwinian tubercle is located, and there it may take any shape—round, straight, or pointed—as illustrated in the drawing. The most singular deformity of the helix is thetubercle of Darwin, which is a little blunt point, projecting from the inwardly folded margin or helix. When present it is developed at birth and, according to Ludwig Meyer, more frequent in men than in women. Fig.40shows ear and tubercle taken from Darwin.[214]These points not only project in toward the centre of the ear, but open a little outwards (Fig.41) from its plane, so as to be visible when the head is viewed from directly in front and behind. They are variable in size, number and somewhat in position (Fig.42), standing either a little higher or lower, and they sometimes occur on one ear and not on the other. Another marked form of ear degeneracy is one in which the ear is developed backward at an angle of about 45° (Fig.43). The general outline of the ear is fairly good. The anti-helix is much larger than it should be. Degeneracy usually extends deeply into the organisation of those in whom this ear is present.
Fig.44illustrates noticeable stigmata. The ear stands at right angles with the head. It is, however, almost as broad as it is long and differs in shape. The outer helix is excessively developed. The scaphoid fossa extends through the lobe, which is continuous with the body of the ear and is not distinct. The root of the helix is excessively developed. There are three Darwinian tubercles on its border. The anti-tragus is undeveloped. The tragus is very small and divided into two parts. The auricle-temporal angle, for functional purposes, should not exceed, according to Buchanan, 30°, or be less than 15°. The difference in this respect is not clear, since free movement of head and body will readilyadjust the auricle to receive sound. For functional purposes it would seem that the construction and shape of the ear, especially the anti-helix and concha, would be of greater importance than its position to the head, since it is necessary to collect the waves of sound for transmission. From a degeneracy standpoint, however, the position of the ear is important. Frigerio,[215]from the examination of several hundred subjects, concludes that the auricle-temporal angle undergoes a gradual progress from below 90° in criminals and the insane to above 90° in apes. He found the large angle very marked in homicides, less so in thieves. There is no question but that Frigerio is correct in regard to this point. In an examination of the ears of 465 boy criminals at Pontiac, it was found that 198 were close to the head, or from 10 to 15°; 152 at an angle of 45°, and 115 at right angles or 90°. Of 1,041 criminals at Elmira 285 were close, 567 at an angle of 45°, and 187 at right angles.
FIG. 46.
FIG. 47.
FIG. 48.
FIG. 49.
Fig.45shows the ear which Hawthorne gives Donatello in theMarble Faun; it has been called the “Satanic” ear, because of the pointed extremities and its narrowness. The helix is rolled upon itself its entire length, giving the impression of great thickness. The anti-helix is excessively developed. Figs.46,47,48(ears of three illegitimate children at birth) show different stages of development as well as marked stigmata. Arrest of development occurs between the fourth and fifth month, owing to the trophic nerve centres being affected by the malnutrition of the mother. Fig.49exhibits the development of a congenital, elephantine ear in monstrosities. The resemblance to the large ear of the orang and chimpanzee is very marked.
The Degenerate Teeth and Jaws
Nextto the ears, the jaws and teeth (as was to be expected from the variability of these organs in allied animals) are most affected by degeneracy. This is particularly true of the vertebrates, especially mammals, as might have been anticipated from their phylogeny. At the head of the vertebrates is man; at the foot is the lancelet (amphioxus), which is perhaps most akin to those semi-vertebrates the ascidians, who, in their larval phase, are higher than when adult, and whose life-history excellently illustrates that potent phase of evolution, degeneracy.
The lancelet has a spinal cord enclosed in a half-gristly canal (the notochord). It is practically destitute of a brain. The cerebral vesicle which represents this is a plain cavity without true subdivision into ventricles. There is no cranium. The eye (central in position) is a mere pigment spot with which it is able to distinguish light from darkness. The nose (behind this) is a small pit, lined with cilia, for purposes of smell. Into this the cerebral vesicle of the larval lancelet opens. The mouth is well guarded against the intrusion of noxious substances whichhave to pass through a vestibule richly provided with sensitive cells, resembling the taste buds of the human mouth. There is no heart. In this, as in the case of the eye, the lancelet is lower than the ascidians, the insects, crustaceans, and many molluscs. It approximates those worms which, despite a very elaborate vascular system, are destitute of a heart, the function of which is performed by contractile blood-vessels. From an embryologic and morphologic standpoint the proximate ancestor of the vertebrates may have been a free swimming animal, intermediate between an ascidian tadpole and the lancelet, and the primordial ancestor, a worm-like animal organised on a level with the star-fish. The vertebrates embryologically develop from this stage to the lampreys; thence to the cartilaginous fish (shark); to the amphibia (frog, toad, axolotl); to the reptiles; and thence to the oviparous mammals (duck-bill and echidna or spiny ant-eater); to the lemurs, and through forms like thePithecanthropus erectusto man. Mammal teeth pass, in evolution, from the simple types found in that oviparous edentate, the spiny ant-eater of Australia, to those of the indeciduous ancestors of the sloths and armadilloes, and their descendants, inclusive of the dolphins and whales, whose teeth, both in the fetal Greenland and adult sperm whale, preserve this old type. (The whales have degenerated from the hoofed mammals to suit their environment.) While, as in the edentates, these teeth may be few, they may also, as in the insectivorous marsupials, approximate those of the reptilia in number (sixty or seventy on a side) and characteristic location.
The evolution of this primitive tooth to the bicuspidand molar type has been explained by two theories: that of concrescence and that of differentiation.[216]
A number of conical teeth, in line as they lie in the jaws of the sperm whale, represent the primitive dentition.[217]In time a number of these teeth, according to the concresent theory, cluster together so as to form the four cusps of a human molar, each one of the whale tooth points forming one of the cusps of the mammalian tooth. Vertically succeeding teeth might also be grouped. What evidence is there in favour of this theory? and what is there against it? All primitive reptiles from which the mammals have descended, and many of the existing mammals, have a large number of isolated teeth of a conical form. Further, by shortening of the jaws, the embryonic germ from which each of the numerous tooth-caps is budded off in course of development could have been brought together in such a manner that any cusps originally stretched out in a line would form groups of a variable number of cusps, according to the more or less complex pattern of the crown. Against the acceptance of this theory stands the fact that cusps quite similar in all respects to each of the cusps which form the angles of the human molar are even now being added to the teeth in certain animals, such as the elephant, whose molar teeth cusps are being thus complicated. In the mesozoic period certain animals with tricuspid teeth occur. According to the theory of concrescence these teeth ought not to show any increase of cusps in later geologic periods, but down through the ages to the present time successors of those animals continue to present a very much larger number of cusps.How is this increase of cusps to be accounted for? Has there been a reserve store of conical teeth to increase the number? Most obviously to every student of the fossil history of cusps there is no reserve store, but new cusps are constantly rising upon the original crown itself by cusp addition.
In the Triassic occur the first mammalia with conical, round, reptilian teeth. There are also some aberrant types which possess complex or multitubercular teeth.
These teeth begin to show the first trace of cusp addition.
In Fig. 1,Plate A, the teeth of the dromatherium of the coal beds of North Carolina occur on the sides of the main cone, cusps or rudimentary cuspules. On either side of the main cone are two cuspules. In the same deposit occurred another animal represented by a single tooth (Fig. 3), in which these cusps are slightly larger. These cusps have obviously been added to the side of the teeth and are now growing. In teeth of the Jurassic period, found in large numbers both in America and in England, but still of very minute size, are observed the same three cusps. These cusps have now taken two different positions; in one case they have the arrangement presented inPlate B. The middle cusp is relatively lower, and the lateral cusps are relatively higher; in fact these cones are almost equal in size. These teeth are termed triconodont, as having three nearly equal cones. But associated with this is the spalacotherium, the teeth of which are represented inPlate A, Fig. 4. This tooth illustrates the transformation of a tooth (triconodont) with three cusps in line into a tooth with three cusps forming a triangle.Here the primitive cusp is the apex of a triangle of which the two lateral cusps are the base. This tooth, in this single genus, is the key of comparison of the teeth of all mammalia. By this can be determined that part of a human molar which corresponds with a conical reptilian tooth. This stage is the triangle stage; the next stage is the development of a heel or spur upon this triangle (see in the amphitherium, Fig. 5). The opossum still distinctly preserves the ancient triangle. Look at it in profile, inside or in top view, and see that the anterior part of the tooth is unmodified. This triangle is traceable through a number of intermediate types. In Miacia (Fig. 6), a primitive carnivore, is a high triangle and a heel; looked at from above (Fig. 6a), the heel is seen to have spread out broader so that it is as broad as the triangle. The three molars of this animal illustrate a most important principle, namely, that the anterior, triangular portion of the crown has been simply levelled down to the posterior portion.
PLATE A.
PLATE B.
These three teeth form a series of intermediate steps between a most ancient molar and the modern molar of the human type. The second tooth is halfway between the first and third. The second molar, seen from above, has exactly the same cusps as the first, so it is not difficult to recognise that each cusp has been directly derived from its fellow. The third tooth of the series (Fig. 7) has lost one of its cusps; it has lost a cusp of the triangle. It is now a tooth where only half the triangle is left on the anterior side and with a very long heel. That tooth has exactly the same pattern as the lower human molar tooth (Fig. 8), the only difference is that the heel is somewhat more prolonged. These teeth belong toone of the oldest fossil monkeys, anaptomorphus. Human lower molars, not very exceptionally, instead of four cusps, have five. The fifth cusp always appears in the middle of the heel, or between the posterior lingual and the posterior buccal. This occurs in monkeys and other animals, but no record exists of the ancient anterior lingual reappearing. The human lower molar, with its low, quadritubercular crown, has hence evolved by addition of cusps and by gradual modelling from a high-crowned, simple, pointed tooth.
Human teeth are of excellent service in the initial determination of degeneracy in the child. For this purpose the teeth should be studied from the first evidence of their development until they are all in place, which occurs normally, in most cases, by the twenty-second year.
Teeth-enamel is formed from the epiblast, and dentine, cementum, pulp (except as to nerve tissue) from the mesoblast. The enamel organs of the first set appear during the seventh week of fœtal life; the dentine bulb during the ninth week. At this period the tooth obtains its periphery. This models the enamel cap which fits over the dentine like a glove. When imperfections in hand or fingers exist these deformities are distinctly observed upon the glove, and in precisely the same manner are observed the different shapes and sizes of the incisors, cuspids, and molars. Calcification of the teeth begins at the seventeenth week of fœtal life. The illustration (Fig.50) shows the progress of calcification and development of the temporary set of teeth. Examination will show that any defect in nutrition, from conception to birth (due to inherited states ormaternal impressions), has been registered upon the teeth. The state of the constitution and the locality register the date of such defects. Thus if the tooth, as a whole, be larger or smaller than normal, or abnormally irregular, taint is undoubtedly inherited from one or both parents. If, on the other hand, there be defect at any part on the crowns of the teeth, and the contour be perfect, the date of malnutrition can be easily determined from this chart. More or less than the normal number of teeth, abnormally placed, demonstrates the existence of inherited defect, since the germs must have been deposited at the period mentioned. No absolute rule can be laid down as to date of the eruption of the teeth. The teeth of the temporary set erupt nearly as follows:
FIG. 50.
FIG. 51. SHOWS LINES OF DEVELOPMENT OF THE PERMANENT TEETH.
The enamel organs and dentine bulb for thepermanent teeth form just before birth (Fig.51) in like manner with the temporary set. They form just above the temporary set on the upper and below on the lower jaw. The permanent molars begin to calcify at the twenty-fifth week of fœtal life. The permanent incisors do not calcify until a year after birth. Any deviation in size or contour of the permanent teeth from the normal must hence be due to defect in nutrition in the dentine bulb, between the fifteenth and twenty-fifth week of fœtal life. Any deviation in calcification (except the cusps of the first permanent molars) must occur after birth. At the third year twenty-four teeth are fairly well calcified. At the fifth year the second permanent molars, and at the eighth year the third molars or wisdom teeth, begin to calcify.
The following table gives the age of eruption of permanent teeth:
Man, at this present stage of evolution, has twenty teeth in his temporary and thirty-two in his permanent set. Any deviation in number is the result of embryonic change occurring between the sixth and fifteenth week, for the temporary teeth, and the fifteenth week and birth for the permanent. The germs of teeth which erupt late in life, and are called third sets, of necessity appear ere birth and are completely formed at the beginning of the secondyear, although they remain protected in the jaw until eruption.
More than twenty teeth in the temporary set, or thirty-two in the permanent set, is hence an atavistic abnormality. From the maxillary and dental standpoint man reached his highest development when well-developed jaws held twenty temporary and thirty-two permanent teeth. Decrease in the numbers of teeth meant, from the dental standpoint, degeneracy, albeit it might mark advance in man’s evolution as a complete being. In the New Mexican Lower Eocene occur monkeys like the lemurarius and limnotherium, each the type of a distinct family. The lemurarius, most nearly allied to the lemurs, is the most generalised monkey yet found. It had forty-four teeth in continuous series, above and below. The limnotherium, while related to the lemurs, had some affinities with the American marmosets. These solved the problem of the origin of the extra teeth (known as supernumeraries) that sometimes occur in man, and demonstrated that man, during his evolution from the lowest monkey, lost twelve teeth. These supernumerary teeth assume two forms; either they resemble the adjoining teeth or are cone-shaped. While they are rarely exactly counterparts, every tooth can be duplicated, as the following illustrations show.
Fig.52illustrates fairly well-formed duplicate central incisors, the normal incisors being outside the dental arch. They are crowded laterally by the large roots of the supernumerary incisors.
FIG. 52.
FIG. 53.
FIG. 54.
Fig.53shows an extra right lateral in a temporary set in the upper jaw. Fig.54an extra right lateral in the permanent set. Fig.55illustrates normally developed supernumerary cuspids which are all grouped together upon the right side, the bicuspid being also duplicated on each side; indeed, all but the molars are duplicate. Fig.56shows supernumerary third molars, easily demarcated from the normal molars. The teeth which fail to approximate their normal neighbours assume the cone shape of the primitive tooth.
FIG. 55.
FIG. 56.
The fact that the cone-shaped tooth, as a rule perfect in construction, is found everywhere in thejaw, but especially in the anterior and posterior part of the mouth, is of much value in outlining tooth and jaw evolution, especially in the degeneracy phase. The upper jaw, being an integral part of the skull and fixed, is, of necessity, influenced by brain and skull growth; hence degeneracy is more detectable in it than in the lower.
FIG. 57.
FIG. 58.
FIG. 59.
FIG. 60.
FIG. 61.
The evolution of the jaw is toward shortening in both directions. This shortening will continue so long as the jaw must be adjusted to a varying environment. The jaw of man having originally contained more teeth than at present, lack of adjustment to environment produces, from the shortening, degeneracy of the jaw and atavism of the teeth. While this may coincide with general advances of the individual, it indicates that he is not yet adjusted to his new environment. The shortening of the upper jaw causes supernumerary, cone-shaped teeth to erupt, in mass, at the extreme ends of the jaw, as shown in the following figures. Fig.57illustrates a cone-shaped tooth between the two central incisors, forcing them out of position. Fig.58shows three supernumerary teeth—a cone-shaped tooth between thecentrallaterals, and the cuspids out of position. The left permanent lateral is at the median line; another cone-shaped tooth remains in the vault, while the supernumerary left lateral is in place. As many as eight are at times to be observed in the anterior vault. Posteriorly these teeth are most often noticed in connection with the third molars, usually on a line with other teeth posterior to the last molar. Fig.59shows two supernumerary teeth in the anterior and two in the posterior part of the left arch; the molars have been extracted. Supernumerary teeth are not confined to these localities, but may be observed at any point in the dental arch (Figs.60and61). The primitive cone-shaped tooth is rarely observed in the lower jaw. In twenty-six years’ practice I have not seen a case. The mobility of the lower jaw preventsthat mal-adjustment to environment present in the upper. The continual shortening, in both directions, of the jaw causes the third molars frequently to wedge in between the angle of the jaw and the second molars, so that eruption, if possible, is difficult.
FIG. 62.
FIG. 63.
FIG. 64.
The third molar is often absent in the English-speaking and Scandinavian races. In 46 per cent. of 670 patients it was missing. Frequently its development is abortive. This tooth, in the struggle for existence, seems destined to disappear. It is more often absent from the upper than the lower jaw. When absent, or badly developed, the jaw is smaller and frequently teeth irregularities, nasal stenosis, hypertrophy of nasal bone and mucous membrane, adenoids and eye disorders coexist. Fig.62shows absence of the left third molar with irregularities of that side of the arch. In Fig.63both third molars are seen to be missing. Anteriorly, the lateral incisors are most often wanting; 14 per cent. of the laterals were wanting in 670 patients. In the progress of evolution man has lost one lateral upon each side of the mouth and the second lateral seems also destined to disappear. In Fig.64theleft lateral incisor has disappeared; and in Fig.65both lateral incisors are absent. Not infrequently does it occur that centrals, cuspids, bicuspids, and even molars are absent, even their germs not being detectable. Fig.66shows three supernumeraries in the anterior part of the mouth and but two molars. The absence of the teeth indicates lack of development of germs, due either to heredity or defective maternal nutrition at the time of conception or during early pregnancy.
FIG. 65.
FIG. 66.
FIG. 67.
Crescent-shaped, bitubercular, and tribucular as well as deformed teeth, tend to be cone-shaped. The malformation of these teeth results from precongenital trophic change in dentine development, dwarfing and notching the cutting and grinding edges of the second set of teeth, of which a familiar example is the so-called Hutchinson’s teeth, usually referred to a syphilitic causation. Hutchinson’s position has, however, been more strongly stated than his words justify, since he admits that in at least one-tenth of the cases this cause could be excluded.
Syphilis only plays the part of a diathetic state profoundly affecting the maternal constitution at the time of dentine development; while these teeth maybe due to secondary results of syphilis, they do not demonstrate syphilitic heredity.
In Fig.67are seen the teeth of an individual affected with constitutional disease (referring to Fig.51it becomes evident that the defective lines represent the respective ages, 2½, 4, and 5 years). The degree of pitting will depend, as a rule, on the severity of the constitutional disorder. In the case just cited, however, although nutrition was but slightly disordered, each tooth shows a tendency to conate. Not infrequently cavities extend completely through the tooth. The cusps of the (permanent) first molars, calcifying at the first year, are usually attacked also, and arrested in development, producing the cone shape. These data, together with the dates of eruption of the temporary and permanent teeth, furnish an absolute basis for calculation as to malnutrition producing excessive or arrested development, not only of the teeth and jaws but all parts of the body.
FIG. 68.
FIG. 69.
FIGS. 70, 71.
Fig.68shows a very degenerate jaw with cone-shaped, malformed bicuspids. The right lateral missing, the cuspids are erupting in the vault and the dental arch is assuming a V-shape. The jaw shows, as a whole, marked arrest in development. Fig.69shows Hutchinson’s teeth. Were the first molars visible, they would present marked contraction of the outer surface with a malformed centre. Referring again to Fig.51, it is observable that trophic changes affected the system at the age of birth. The outer surface exhibits a tendency to take the cone shape. Figs.70,71,72,73, and the molars in Fig.66, exhibit malformations that assume the cone shape and the centre frequently associated with this type of teeth. The coincidence in form between Hutchinson’s and malformed teeth and those of the chameleon suggests that tropho-neurotic change produces atavistic teeth. Fig.74illustrates the tendency of human bicuspids (when there is no antagonism) to rotateone-fourth round, thus again indicating an atavistic tendency toward the teeth of the chameleon. Fig.75exhibits extreme atavism; all teeth anterior to the molars are cone-shaped. The third molars are missing and would, probably, never erupt. In Fig.76appears more marked atavism. The upper and lower are both cone-shaped, and the superior first bicuspid exhibits tendency thereto. The right superior second bicuspid, second and third molars, the right inferior first and second bicuspids, with second and third molars are missing. The same condition, probably, exists on the left side. The space in the upper jaw is due to the insufficient width of the teeth. Alternation of teeth in the upper and lower jaw is a reptilian feature.
FIG. 74.
FIG. 75.
Fig.76furnishes excellent illustration of the principles already stated. In degenerate jaws every tooth in the jaw, at one point or another, may display rudimentary cusps. On the incisors they are always to be found on the lingual surface.
FIG. 76.
FIG. 77.
Fig.77illustrates the centrals with two rudimentary cusps, the laterals with one, and the cuspids with one also. Fig.78represents cusps upon the lingual surface of the molars. The cuspids are notunlike the lower cuspids with a rudimentary lingual cusp.
FIG. 78.
There is a gradation from central incisors toward the bicuspids, in evolution. This grading of form is not observed in passing from the cuspid to the bicuspid in man. But the cuspid often presents a cingulum on the lingual face that inclines it toward the bicuspid forms in lower mammals, like the mole, and the first premolar, or bicuspid, is then more caniniform, the inner tubercle being much more reduced. This inner tubercle is very variable and erratic as to its position. It appears as far front as the centrals and is often present on the lingual face of the laterals of man. The lingual tubercle is very constant on the first bicuspid of man and is as well developed as the buccal. But in some lower forms, as in the lemurs, it is quite deficient. It attains the highest developmentonly in the anthropoids and man. Considering these stages of development, the grading from the cuspid to the bicuspid forms was more gradual in the earlier species than in the later, where the individual teeth have taken on special development.
FIG. 79.
The skull of a degenerate girl who died from tuberculosis, at thirteen years, presented, among other stigmata, a cusp on the external surface of a right inferior cuspid. In Fig.79, where every tooth is present, a most remarkable display of cusps occurs. The cusps upon the cutting and grinding edges are not obliterated. Commencing with the left superior central incisors, three cusps are present with a rudimentary palatine cusp. The laterals also show three cusps, while the cuspid has two very distinct. The first and second bicuspids have tubercular cusps, theybeing in line. The buccal cusps upon the molars, two or three, and are still in position. The palatine cusps are worn away. The same is the case upon the opposite side, except that the cuspid has cusps that have fused together, leaving a small projection upon the mesial side and a rudimentary palatine cusp. The cusp upon the third molar is lost. In another case (Fig.61) the primitive cone teeth are seen trying to shape themselves into incisors. The lateral incisors, cuspids and bicuspids are still cone-shaped. The first permanent molar is fairly formed while the second molars are still in a primitive condition.
Degenerate teeth unite in twos, threes, fours, and fives. These single, cone-shaped teeth grow together and form bicuspids and molars. The germ of any two normal teeth may intermingle and unite; not only are the crowns found united with separate roots, but crowns and roots are united throughout.
Figs.80and81show two superior, central and lateral incisors joined together throughout the entire length of crown and root. In Fig.82two lower incisors are united throughout. Fig.83shows a cuspid with two roots. George T. Carpenter, of Chicago, has a right superior, second bicuspid with three well formed roots. Fig.84illustrates two bicuspids united at the crowns. Fig.85shows two molars perfectly united. Fig.86illustrates central and lateral incisors of the permanent set perfectly united. Fig.87shows two molars united. Fig.88a molar and supernumerary taking the cone-shape with deformed centre. Fig.89shows three malformed teeth, each coated and completely united. It is not uncommon to find three molars united together, as, for instance, the second, third, and supernumerarymolars. C. V. Rosser, of Atlanta, Georgia, has two small molars and a supernumerary cuspid perfectly united, from crown to root, and these three further united to the roots of a well-formed molar.