Suborder 1:Phaenocystes, Gurley. Spores relatively large, with generally two or four polar-capsules, visible in the freshClassification.condition. There are nearly always two spores formed in each pansporoblast.Section (a):Disporea. Only two spores (i.e.one pansporoblast) produced in each individual trophozoite. The greatest length of the spore is at right angles to the plane of the suture.One family,Ceratomyxidae, including two genera,Ceratomyxa(fig. 3, B) andLeptotheca, typically “free” parasites, mostly from the gall bladders of fishes. The valves of the spore in the former genus are prolonged into hollow cones. The type-species of this genus isC. sphaerulosa, fromMustelusandGaleus; that ofLeptothecaisL. agilis, fromTrygon.Section (b):Polysporea. More than two spores, generally very many, are produced typically by each individual trophozoite. The greatest length of the spore is usually in the sutural plane.Family,Myxidiidae. Spores with two polar-capsules, and without an iodinophilous vacuole in the sporoplasm. Mostly “free”parasites. Gen.Sphaerospora. Four or five species are known, from the kidneys or gall bladder of fishes (fig. 3, A). One,S. elegans, is interesting in that it affords a transition between the two sections, being disporous. Gen.Myxidium; spores elongated and fusiform, with a polar capsule at each extremity. The best-known species isM. lieberkühnii, from the urinary bladder of the pike. One or two species occur in reptiles. Other genera areSphaeromyxa,Cystodiscus,MyxosomaandMyxoproteus.Family,Chloromyxidae. Spores with four polar capsules and no iodinophilous vacuole. One genus,Chloromyxum, of which several species are known; the type beingC. leydigi, from the gall bladder of various Elasmobranchs (fig. 7, B).Fig.7.—A. Spore ofCeratomyxa sphaerulosa, Thél. (par.MustelusandGaleus), × 750, after Thélohan.sp.p, Sporoplasm;p.c, polar capsules;s, suture;x, “irregular, pale masses, of undetermined origin.”From Lankester’sTreatise on Zoology, vol. Protozoa.B. Spores ofChloromyxidae, after Thélohan.a,Chloromyxum leydigi, Ming., seen from the sutural aspect, × 2250;b,C. caudatum, Thél., × 1900.p.c, Polar capsules;s, suture;f, filaments;p.s, tail-like process of the spore envelope.From Wasielewski’sSporozoenkunde.C. Spores ofMyxobolus ellipsoides, Thél. The spores on the left and right are lying with the sutural plane horizontal, that in the middle with the sutural plane vertical.Family,Myxobolidae. Spores with two polar-capsules (exceptionally one), and with a characteristic iodinophilous vacuole in the sporoplasm. Typically tissue parasites of Teleosteans, often very dangerous. GenusMyxobolus. Spores oval or rounded, without a tail-like process. Very many species are known, which are grouped into three subsections: (a) forms with only one polar-capsule, such asM. piriformis, of the tench; (b) forms with two unequal capsules,e.g.M. disparfromCyprinusandLeuciscus; and (c) the great majority of species with two equal polar-capsules, includingM. mülleri, the type-species, from different fish,M. cypriniandM. pfeifferi, the cause of deadly disease in carp and barbel respectively and others. Other genera areHenneguyaandHoferellus, differing fromMyxobolusin having, respectively, one or two tail-like processes to the spore.Lentospora, according to Plehn (37), lacks an iodinophilous vacuole.FamilyCoccomyxidae. The pansporoblasts produce (probably) only one spore. Spore oval, large (14 μ by 5.5 μ), with a single very large polar-capsule. Sporoplasm with no vacuole. Single genusCoccomyxa, with the characters of the family. One species,C. morovi, Léger and Hesse, from the gall bladder of the sardine. The spore greatly resembles a Cryptocystid spore.Suborder 2:Cryptocystes, Gurley (=Microsporidia, Balbiani). Spores minute, usually pear-shaped, with only one polar-capsule, which is visible only after treatment with reagents. The number of spores formed in each pansporoblast varies greatly in different forms.Section (a):Polysporogenea. The trophozoite produces numerous pansporoblasts, each of which gives rise to many spores. GenusGlugea, with numerous species, of which the best-known isG. anomala, from the stickleback (fig. 1). The genusMyxocystis, which has been shown by Hesse (24) to be a true Microsporidian, is placed by Perez in this section, but this is a little premature, as Hesse does not describe the exact character of the sporulation,i.e.with regard to the number of pansporoblasts and the spores they produce.Section (b):Oligosporogenea. The trophozoite becomes itself the (single) pansporoblast. InPleistophora, the pansporoblast produces many spores;P. typicalis, from the muscles of various fishes (fig. 2), is the type-species. InThelohania, eight spores are formed; the different species are parasitic in Crustacea. InGurleya, parasitic inDaphnia, only four are formed; and, lastly, inNosema(exs.N. pulvis, fromCarcinus, and, most likely,N. bombycis, of the silkworm), each pansporoblast produces only a single spore.
Suborder 1:Phaenocystes, Gurley. Spores relatively large, with generally two or four polar-capsules, visible in the freshClassification.condition. There are nearly always two spores formed in each pansporoblast.
Section (a):Disporea. Only two spores (i.e.one pansporoblast) produced in each individual trophozoite. The greatest length of the spore is at right angles to the plane of the suture.
One family,Ceratomyxidae, including two genera,Ceratomyxa(fig. 3, B) andLeptotheca, typically “free” parasites, mostly from the gall bladders of fishes. The valves of the spore in the former genus are prolonged into hollow cones. The type-species of this genus isC. sphaerulosa, fromMustelusandGaleus; that ofLeptothecaisL. agilis, fromTrygon.
Section (b):Polysporea. More than two spores, generally very many, are produced typically by each individual trophozoite. The greatest length of the spore is usually in the sutural plane.
Family,Myxidiidae. Spores with two polar-capsules, and without an iodinophilous vacuole in the sporoplasm. Mostly “free”parasites. Gen.Sphaerospora. Four or five species are known, from the kidneys or gall bladder of fishes (fig. 3, A). One,S. elegans, is interesting in that it affords a transition between the two sections, being disporous. Gen.Myxidium; spores elongated and fusiform, with a polar capsule at each extremity. The best-known species isM. lieberkühnii, from the urinary bladder of the pike. One or two species occur in reptiles. Other genera areSphaeromyxa,Cystodiscus,MyxosomaandMyxoproteus.
Family,Chloromyxidae. Spores with four polar capsules and no iodinophilous vacuole. One genus,Chloromyxum, of which several species are known; the type beingC. leydigi, from the gall bladder of various Elasmobranchs (fig. 7, B).
Family,Myxobolidae. Spores with two polar-capsules (exceptionally one), and with a characteristic iodinophilous vacuole in the sporoplasm. Typically tissue parasites of Teleosteans, often very dangerous. GenusMyxobolus. Spores oval or rounded, without a tail-like process. Very many species are known, which are grouped into three subsections: (a) forms with only one polar-capsule, such asM. piriformis, of the tench; (b) forms with two unequal capsules,e.g.M. disparfromCyprinusandLeuciscus; and (c) the great majority of species with two equal polar-capsules, includingM. mülleri, the type-species, from different fish,M. cypriniandM. pfeifferi, the cause of deadly disease in carp and barbel respectively and others. Other genera areHenneguyaandHoferellus, differing fromMyxobolusin having, respectively, one or two tail-like processes to the spore.Lentospora, according to Plehn (37), lacks an iodinophilous vacuole.
FamilyCoccomyxidae. The pansporoblasts produce (probably) only one spore. Spore oval, large (14 μ by 5.5 μ), with a single very large polar-capsule. Sporoplasm with no vacuole. Single genusCoccomyxa, with the characters of the family. One species,C. morovi, Léger and Hesse, from the gall bladder of the sardine. The spore greatly resembles a Cryptocystid spore.
Suborder 2:Cryptocystes, Gurley (=Microsporidia, Balbiani). Spores minute, usually pear-shaped, with only one polar-capsule, which is visible only after treatment with reagents. The number of spores formed in each pansporoblast varies greatly in different forms.
Section (a):Polysporogenea. The trophozoite produces numerous pansporoblasts, each of which gives rise to many spores. GenusGlugea, with numerous species, of which the best-known isG. anomala, from the stickleback (fig. 1). The genusMyxocystis, which has been shown by Hesse (24) to be a true Microsporidian, is placed by Perez in this section, but this is a little premature, as Hesse does not describe the exact character of the sporulation,i.e.with regard to the number of pansporoblasts and the spores they produce.
Section (b):Oligosporogenea. The trophozoite becomes itself the (single) pansporoblast. InPleistophora, the pansporoblast produces many spores;P. typicalis, from the muscles of various fishes (fig. 2), is the type-species. InThelohania, eight spores are formed; the different species are parasitic in Crustacea. InGurleya, parasitic inDaphnia, only four are formed; and, lastly, inNosema(exs.N. pulvis, fromCarcinus, and, most likely,N. bombycis, of the silkworm), each pansporoblast produces only a single spore.
aandb,Pleistophora typicalis, Gurley;ain the fresh condition,bafter treatment with iodine water, causing extrusion of the filament.
candd,Thelohania octospora, Henneguy;cfresh,dtreated with ether.
e,Glugea depressa, Thél., fresh.
f,G. acuta, Thél.
2. Order—Actinomyxidia.This order comprises a peculiar group of parasites, first described by A. Stolc in 1899, which are restricted to Oligochaete worms of the familyTubificidae. Most forms attack the intestinal wall, often destroying its epithelium over considerable areas; but one genus,Sphaeractinomyxon, inhabits the body-cavity of its host. The researches of Caullery and Mesnil (10-12) and of Léger (28and29) have shown that the parasites exhibit the typical features of the Endospora, and the spores possess the characteristic polar-capsules of the Myxosporidian spore, but differ therefrom by their more complicated structure.
The growth and development of an Actinomyxidian have been recently worked out by Caullery and Mesnil in the case ofSphaeractinomyxon stolci. A noteworthy point is the differentiation of an external (covering) cellular layer, which affords, perhaps, the nearest approach to distinct tissue-formation known among Protozoa. This envelope is formed soon after nuclear multiplication of the young trophozoite has begun, and is constituted by two nuclei and a thin, peripheral layer of cytoplasm. It remains binuclear throughout the entire period of development, and serves as a delicate cyst-membrane. The multiplication of the internal nuclei is accompanied by a corresponding division of the cytoplasm; so that instead of a multinucleate or plasmodial condition, distinct uninucleate cellules are formed, up to sixteen in number. These cellules, as a matter of fact, are sexual elements or gametes; and eight of them can be distinguished from the other eight by slight differences in the nuclei. The gametes unite in couples, each couple being most probably composed of dissimilar members: in other words, conjugation is slightly anisogamous. Each of these eight copulae gives rise to a spore.
As the name of the order implies, there are always eight spores formed. These differ from other Endosporan spores in having invariably a ternary symmetry and constitution (fig. 9). The wall of the spore is composed of three valves, each formed from an enveloping cell, and three capsular cells, placed at the upper or anterior pole, and containing each a polar-capsule, visible in the fresh condition. The valves are usually prolonged into processes or appendages, whose form and arrangement characterize the genus; but inSphaeractinomyxonthe spore is spherical and lacks processes. The sporoplasm may be either a plasmodial mass, with numerous nuclei, or may form a certain number of uninuclear sporozoites. A remarkable feature in the development of the spore is that the germinal tissue (sporoplasm) arises separate from and outside the cellules which give rise to the spore-wall; later, when the envelopes are nearly developed, the sporoplasm penetrates into the spore.
Four genera have been made known. (1)Hexactinomyxon, Stolc. Spores having the form of an anchor with six arms; sporoplasm plasmodial, situate near the anterior pole of the spore. One sp.H. psammoryctis, fromPsammoryctes. (2)Triactinomyxon, St. Spores having the form of an anchor with three arms; distinct sporozoites, disposed near the anterior pole.T. ignotum, with eight spores, fromTubifex tubifex, and also from an unspecified Tubificid; another sp., unnamed, with 32 sporozoites, also fromT. t.(3)Synactinomyxon, St. Spores united to one another, each having two aliform appendages; sporoplasm plasmodial. One sp.,S. tubificis, fromT. rivulorum. (4)Sphaeractinomyxon, C. and M. Spores spherical, without aliform prolongations; sporoplasm gives rise to very manysporozoites, occupying the whole spore. One sp.,S. stolci, fromClitellioandHemitubifex.
Four genera have been made known. (1)Hexactinomyxon, Stolc. Spores having the form of an anchor with six arms; sporoplasm plasmodial, situate near the anterior pole of the spore. One sp.H. psammoryctis, fromPsammoryctes. (2)Triactinomyxon, St. Spores having the form of an anchor with three arms; distinct sporozoites, disposed near the anterior pole.T. ignotum, with eight spores, fromTubifex tubifex, and also from an unspecified Tubificid; another sp., unnamed, with 32 sporozoites, also fromT. t.(3)Synactinomyxon, St. Spores united to one another, each having two aliform appendages; sporoplasm plasmodial. One sp.,S. tubificis, fromT. rivulorum. (4)Sphaeractinomyxon, C. and M. Spores spherical, without aliform prolongations; sporoplasm gives rise to very manysporozoites, occupying the whole spore. One sp.,S. stolci, fromClitellioandHemitubifex.
a,Hexactinomyxon psammoryctis(par.Psammoryctes barbatus).
b,Synactinomyxon tubificis(par.Tubifex rivulorum); the mass of united spores.
c,Triactinomyxon ignotum(par.Clitellio, sp.).
d, Upper portion ofHexactinomyxon, showing two of the three polar capsules, one with filament discharged.
3. Order—Sarcosporidia.With the exception of one or two forms occurring in reptiles, these parasites are always found in warm-blooded Vertebrates, usually Mammals. They are of common occurrence in domestic animals, such as pigs, sheep, horses and (sometimes) cattle. A Sarcosporidian has also been described from man. The characteristic habitat is the striped muscle, generally of the oesophagus (fig. 10, A) and heart, but in acute cases the parasites overrun the general musculature. When this occurs, as often happens in mice, the result is usually fatal. Unless, however, the organisms thus spread throughout the body, the host does not appear to suffer any serious consequences. In addition to the effects produced by the general disturbance to the tissues, the attacked animals have apparently to contend—at any rate in the case ofSarcocystis tenellain the sheep—with a poison secreted by the parasite. For Laveran and Mesnil (27) have isolated a toxine from this form, which they have termed sarcocystin.
In the early stages of growth, a Sarcosporidian appears as an elongated whitish body lodged in the substance of a muscle-fibre; this phase has long been known as a “Miescher’s tube,” orMiescheria. The youngest trophozoites that have been yet observed (by Bertram, 1) were multinucleate (fig. 11, A), but there is no reason to doubt that they begin life in a uninuclear condition. The protoplasm is limited by a delicate cuticle. With growth, organellae corresponding to the Myxosporidian pansporoblasts are formed by the segregation internally of little uninuclear spheres of protoplasm. At the same time, a thick striated envelope is developed around the parasite, which later comes to look like a fur of fine filaments. The probable explanation of this feature (given by Vuillemin,44) is that it is due to the partial breaking down of a stiff, vertically (or radially) striated external layer (fig. 12, A), such as is seen inMyxidium lieberkühnii. Immediately internal to this is a thin, homogeneous membrane, which sends numerous partitions or septa inwards; these divide up the endoplasm into somewhat angular chambers or alveoli (fig. 12). In each chamber is a pansporoblast, which divides up to produce many spores; hence the spores formed from different pansporoblasts are kept more or less separate. The pansporoblasts originate, in a growing Sarcosporidian, at the two poles of the body, where the peripheral endoplasm with its nuclei is chiefly aggregated. More internally, spore-formation is in progress; and in the centre, pansporoblasts full of ripe spores are found.
By this time the parasite has greatly distended the muscle-fibre in which it has hitherto lain, absorbing, with its growth, practically all the contractile-substance, until it is surrounded only by the sarcolemma and sarcoplasm. It next passes into the adjacent connective-tissue, and in this phase has been distinguished fromMiescheriaasBalbiania, under the impression that the two forms were quite distinct. In the later stages, the parasite may become more rounded, and a cyst may be secreted around it by the host’s tissue. In these older forms, the most centrally placed spores degenerate and die, having become over-ripe and stale.
With regard to the spores themselves and what becomes of them, our knowledge is defective. Two kinds of reproductive germ have been described, termed respectivelygymnospores(so-called sporozoites, “Rainey’s corpuscles”) andchlamydospores, or simply spores. It seems probable that the former serve for endogenous or auto-infection, and the latter for infecting fresh hosts. Unfortunately, however, both kinds of germ are not yet known in the case of any one species. The gymnospores, which are the more commonly found (e.g.inS. muris,S. miescherianaof the pig, and other forms), are small sickle-shapedor reniform bodies which are more or less amoeboid, and capable of active movement at certain temperatures. They appear to be naked, and consist of finely granular protoplasm, containing a single nucleus and one or two vacuoles. The chlamydospores, or true spores, occur inS. tenellaof sheep (fig. 13), and have been described by Laveran and Mesnil (26). They also are falciform, but one extremity is rounded, the other pointed. There is a very thin, delicate membrane, most unlike a typical, resistant spore-wall; and the spores themselves are extremely fragile and easily acted upon and deformed by reagents, even by distilled water. The rounded end of the spore contains a large nucleus, while at the other end is an oval, clear space, which, in the fresh condition, shows a distinct spiral striation. The exact significance of this structure has been much debated. In position and appearance it recalls the polar-capsule of a Myxosporidian spore. The proof of this interpretation would be the expulsion of a filament on suitably stimulating the spore; while, however, some investigators have asserted that such a filament is extruded, this cannot be regarded as at all certain. Hence it is still doubtful whether this striated body really corresponds to a polar-capsule.
a, Spore in the fresh condition, showing a clear nucleus (n) and a striated body or capsule (c).
b, Stained spore; the nucleus (n) shows a central karyosome; the striations of the polar capsule (c) are not visible.
Nothing whatever is known as to the natural means by which infection with Sarcosporidia is brought about. Smith (39) showed that mice can be infected withSarcocystis murisby simply feeding them on the flesh of infected mice. It is not very likely, however, that this represents the natural mode, even in the case of mice; and it certainly cannot do so in the case of Herbivora. The difficulty in the way is the delicacy of the spores, which seem totally unfitted to withstand external conditions. It may be that some alternative (intermediate) host is concerned in dispersal; but this has yet to be ascertained.
All known Sarcosporidia are included in a single genusSarcocystis, Lank. (=Miescheria+Balbiania, Blanchard.) Some of the principal species are:S. miescheriana, from pigs;S. tenella, from sheep;S. bertrami, from horses;S. blanchardi, from Bovines;S. muris, from mice;S. platydactyli, from the gecko; and lastly,S. lindemanni, described from man.
All known Sarcosporidia are included in a single genusSarcocystis, Lank. (=Miescheria+Balbiania, Blanchard.) Some of the principal species are:S. miescheriana, from pigs;S. tenella, from sheep;S. bertrami, from horses;S. blanchardi, from Bovines;S. muris, from mice;S. platydactyli, from the gecko; and lastly,S. lindemanni, described from man.
4. Order—Haplosporidia.The Sporozoa included in this order are characterized by the general simplicity of their development, and by the undifferentiated character of their spores. The order includes a good many forms, whose arrangement and classification have been recently undertaken by Caullery and Mesnil (15), to whom, indeed, most of our knowledge relating to the Haplosporidia is due. The habitat of the parasites is sufficiently varied; Rotifers, Crustacea, Annelids and fishes furnishing most of the hosts. A recent addition to the list of Protozoa causing injury to man, a Haplosporidian, has been described by Minchin and Fantham (29d), who have termed the parasiteRhinosporidium, from its habitat in the nasal septum, where it produces pedunculate tumours.
a, Young form with opaque, evenly-granulated protoplasm and few refringent granules; the nuclei (n) are small, and appear to be surrounded each by a clear space.
bandc, Full-grown specimens with large nuclei and clearer protoplasm, containing numerous refringent granules (r. gr.).
dande, Morula stages, derived frombandcby division of the body into segments centred round the nuclei, each cell so formed being a spore. Between the spores a certain amount of intercellular substance or residual protoplasm is left, in which the refringent granules seem to be embedded. The morula may break up forthwith and scatter the spores, or may first round itself off and form a spherical cyst with a tough, fairly thick wall.
f, Empty, slightly shrunken cyst, from which the spores have escaped.
g, Free spore or youngest unicellular trophozoite.
h,i,j, Commencing growth of the trophozoite, with multiplication of the nuclei, which results ultimately in forms such asaandb.
Bertramia, a well-known parasite of the body-cavity of Rotifers, will serve very well to give a general idea of the life-cycle so far as it has yet been made out (fig. 14). The trophozoite begins life as a small, rounded uninucleate corpuscle, which as it grows, becomes multinucleate. The multinuclear body generally assumes a definite shape, often that of a sausage. Later, the protoplasm becomes segregated around each of the nuclei, giving the parasite a mulberry-like aspect; hence this stage is frequently known as a morula. The uninuclear cellules thus formed are the spores, which are ultimately liberated by the break-up of the parent body. Each is of quite simple, undifferentiated structure, possesses a large, easily-visible nucleus, and gives rise in due course to another young trophozoite. In some instances, as described byMinchin, the sporulating parasite becomes rounded off and forms a protective cyst, doubtless for the protection of the spores during dissemination.
In some forms (e.g.HaplosporidiumandRhinosporidium) the spore-mother-cells, instead of becoming each a single spore, as inBertramia, give rise to several, four in the first case, many in the latter. Sometimes, again, the spore, while preserving the essentially simple character of the sporoplasm, may be enclosed in a spore-case; this may have the form of a little box with a lid or operculum, as in some species ofHaplosporidium, or may possess a long process or tail, as inUrosporidium(fig. 15).
TheHaplosporidiaare divided by Caullery and Mesnil into three families,Haplosporidiidae,BertramiidaeandCoelosporidiidae; one or two genera are also included whose exact position is doubtful.(a)Haplosporidiidae: 3 genera,Haplosporidium, type-speciesH. heterocirri;Urosporidium, with one sp.,U. fuliginosum; all parasitic in various Annelids; andAnurosporidium, with the speciesA. pelseneeri, from the sporocysts of a Trematode, parasitic onDonax.From Caullery and Mesnil,Archives de zoologie expérimentale, vol. 4, 1905, by permission of Schleicher Frères et Cie, Paris.Fig.15.—Spores of various Haplosporidia.1.Haplosporidium heterocirri:a, on liberation;b, after being in sea-water.2,H. scolopli.3,H. vejdovskii.4,Urosporidium fuliginosum:a, surface-view;b, side-view. × 1000.(b)Bertramiidae: 2 genera,Bertramia, withB. capitellaefrom an Annelid andB. asperospora, the Rotiferan parasite above described; andIchthyosporidium, withI. gasterophilumandI. phymogenes, parasitic in various fish.(c)Coelosporidiiae: generaCoelosporidium, type-speciesC. chydoriclola; andPolycaryum, type-speciesP. branchiopodianum. These forms are parasitic in small Crustacea. The genusBlastulidiumis referred, doubtfully, by Caullery and Mesnil to this family; but certain phases of this organism seem to indicate rather a vegetable nature.The genusRhinosporidiumshould probably be placed in a distinct family. The only species so far described isR. kinealyifrom the nasal septum of man, to which reference has above been made. Another form,Neurosporidium cephalodisci, agreeing in some respects withRhinosporidium, has been described by Ridewood and Fantham (37a) from the nervous system ofCephalodiscus.A parasite whose affinities are doubtful, but which is regarded by Caullery and Mesnil as allied to the Haplosporidia, is the curious parasite originally described by Schewiakoff as “endoparasitic tubes” ofCyclops; it has been named by Caullery and Mesnil,Scheviakovella. This organism is remarkable in one or two ways: it possesses a contractile vacuole; the amoeboid trophozoites tend to form plasmodia; and the spores, of the usual simple type, may apparently divide by binary fission.
TheHaplosporidiaare divided by Caullery and Mesnil into three families,Haplosporidiidae,BertramiidaeandCoelosporidiidae; one or two genera are also included whose exact position is doubtful.
(a)Haplosporidiidae: 3 genera,Haplosporidium, type-speciesH. heterocirri;Urosporidium, with one sp.,U. fuliginosum; all parasitic in various Annelids; andAnurosporidium, with the speciesA. pelseneeri, from the sporocysts of a Trematode, parasitic onDonax.
1.Haplosporidium heterocirri:a, on liberation;b, after being in sea-water.
2,H. scolopli.
3,H. vejdovskii.
4,Urosporidium fuliginosum:a, surface-view;b, side-view. × 1000.
(b)Bertramiidae: 2 genera,Bertramia, withB. capitellaefrom an Annelid andB. asperospora, the Rotiferan parasite above described; andIchthyosporidium, withI. gasterophilumandI. phymogenes, parasitic in various fish.
(c)Coelosporidiiae: generaCoelosporidium, type-speciesC. chydoriclola; andPolycaryum, type-speciesP. branchiopodianum. These forms are parasitic in small Crustacea. The genusBlastulidiumis referred, doubtfully, by Caullery and Mesnil to this family; but certain phases of this organism seem to indicate rather a vegetable nature.
The genusRhinosporidiumshould probably be placed in a distinct family. The only species so far described isR. kinealyifrom the nasal septum of man, to which reference has above been made. Another form,Neurosporidium cephalodisci, agreeing in some respects withRhinosporidium, has been described by Ridewood and Fantham (37a) from the nervous system ofCephalodiscus.
A parasite whose affinities are doubtful, but which is regarded by Caullery and Mesnil as allied to the Haplosporidia, is the curious parasite originally described by Schewiakoff as “endoparasitic tubes” ofCyclops; it has been named by Caullery and Mesnil,Scheviakovella. This organism is remarkable in one or two ways: it possesses a contractile vacuole; the amoeboid trophozoites tend to form plasmodia; and the spores, of the usual simple type, may apparently divide by binary fission.
5. There remain, lastly, certain forms, which are conveniently grouped together as “Sporozoaincertae sedis,” either for the reason that it is impossible to place them in any of the well-defined orders, or because their life-cycle is at present too insufficiently known. Serosporidia is the name given by Pfeiffer to certain minute parasites of the body-cavity of Crustacea; they includeSerosporidium,BlanchardinaandBotellus.Lymphosporidium, a form with distributed nucleus, causing virulent epidemics among brook-trout, is considered by Calkins(3) to be suitably placed here. Another parasite of lymphatic spaces and channels is the remarkableLymphocystis, described by Woodcock (46), from plaice and flounders, which in some respects rather recalls a Gregarine. The group Exosporidia was founded by Perrier to include a peculiar organism, ectoparasitic on Arthropods, to which the name ofAmoebidiumhad been given by Cienkowsky. It has recently been shown, however, that this organism is most probably an Alga. Another genus,Exosporidium, described by Sand (38), is placed at present in this group. For details of the structure of these forms and others likeSiedleckia,Toxosporidium,ChitoniciumJoyeuxellaandMetschnikovella, a comprehensive treatise on the Sporozoa, such as that of Minchin, should be consulted.
To complete this article, it will be sufficient to mention various enigmatical bodies, associated with different diseases, which are regarded by their describers as Protozoa. Among such is the “Histosporidium carcinomatosum” of Feinberg, which he finds in cancerous growths.Cytoryctes, the name given to “Guarnieri’s bodies” in small-pox and vaccinia, has been recently investigated by Calkins (3a), who has described a complex life-cycle for the alleged parasite. Other workers, however, such as Siegel, give a quite different account of these bodies, and, moreover, find similar ones in scarlet-fever, syphilis, &c.; while yet others (e.g.Prowazek) deny that they are parasitic organisms at all.
Bibliography.—(For general works see underSporozoa.) (1) Bertram, “Beiträge zur Kenntnis der Sarcosporidien,”Zool. Jahrb. Anat.5, 1902; (2) L. Brasil, “Joyeuxella toxoides,” (n.g., n.sp.),Arch. zool. exp.N. et R. (3) 10, p. 5, 7 figs., 1902; (3) G.N. Calkins, “Lymphosporidium truttae,” (n.g., n.sp.),Zool. Anz. 23, p. 513, 6 figs., 1903; (3a)ib.The Life-History of Cytoryctes Variolae; Guarnieri, “Studies path. etiol. variola,”J. Med. Research(Boston, 1904), p. 136, 4 pls.; (3b) M. Caullery and A. Chappellier, “Anurosporidium pelseneeri, (n.g., n.sp.), Haplosporidie,” &c.,C. R. soc. biol.60, p. 325, 1906; (4) M. Caullery and F. Mesnil, “Sur un type nouveau” (Metchnikovella, n.g.),C. R. ac. sci.125, p. 787, 10 figs., 1897; (5)ib.“Sur trois Sporozoaires parasites de la Capitella,”C. R. soc. biol. 49, p. 1005, 1877; (6)ib.“Sur un Sporozoaire aberrant” (Siedleckia, n.g.),op. cit.50, p. 1093, 7 figs., 1898; (7)ib.“Sur le genre Aplosporidium” (nov.),op. cit.51, p. 789, 1899; (8)ib.“Sur les Aplosporidies,”C. R. ac. sci.129, p. 616, 1899; (9)ib.“Sur les parasites intimes des Annélides” (Siedleckia,Toxosporidium), C. R. ass. franç., 1899, p. 491, 1900; (10)ib.“Sur un type nouveau (Sphaeractinomyxon, n.g.) d’Actinomyxidies,”C. R. soc. biol.56, p. 408, 1904; (11)ib.“Phénomènes de sexualité dans le développement des Actinomyxidies,”op. cit.58, p. 889, 1905; (12)ib.“Recherches sur les Actinomyxidies,”Arch. Protistenk.6, p. 272, pl. 15, 1905; (13)ib.“Sur quelques nouvelles Haplosporidies d’Annélides,” C. R. soc. biol. 58, p. 580, 6 figs., 1905; (14)ib.“Sur des Haplosporidies parasites de poissons marins,”ib.p. 640, 1905; (15)ib.“Recherches sur les Haplosporidies,”Arch. zool. exp.(4) 4, p. 101, pls. 11-13, 1905; (16) L. Cohn, “Über die Myxosporidien von Esox lucius,”Zool. Jahr. Anat. 9, p. 227, 2 pls., 1896; (17)ib.“Zur Kenntniss der Myxosporidien,” Centrbl. Bakt. 1, Orig. 32, p. 628, 3 figs., 1902; (18)ib.“Protozoen als Parasiten in Rotatorien,” Zool. Anz. 25, p. 497, 1902; (19) F. Doflein, “Über Myxosporidien,” Zool. Jahr. Anat. 11, p. 281, 6 pls., 1898; (20)ib.“Fortschritte auf dem Gebiete der Myxosporidienkunde,”Zool. Centrbl. 7, p. 361, 1899; (21) R. Gurley, “The Myxosporidia,”Bull. U.S. Fish. Comm., 1892, p. 65, 47 pls., 1894; (22) E. Hesse, “Sur une nouvelle Microsporidie tétrasporée du genre Gurleya,”C. R. soc. biol.55, p. 495, 1903; (23)ib.“Thelohania légeri” (n.sp.),op. cit.57, pp. 570-572, 10 figs., 1904; (24)ib.“Sur Myxocystis Mrazeki Hesse,” &c., op. cit. 58, p. 12, 9 figs., 1905; (25) A. Laveran and F. Mesnil, “Sur la multiplication endogène des Myxosporidies,”op. cit.54, p. 469, 5 figs., 1902; (26)ib.“Sur la morphologie des Sarcosporidies,”op. cit.51, p. 245, 1899; (27)ib.“De la Sarcocystin,”op. cit.p. 311, 1899; (28) L. Léger, “Sur la sporulation du Triactinomyxon,”op. cit.56, p. 844, 4 figs., 1904; (29)ib.“Considérations sur ... les Actinomyxidies,”op. cit.p. 846, 1904; (29a) L. Léger and E. Hesse, “Sur une nouvelle Myxosporidie, Coccomyxa, n.g.,”C. R. ac. sci., 1st July 1907; (29b)ib.“Sur la structure de la paroisporale des Myxosporidies,”op. cit.142, p. 720, 1906; (29c) A. Lutz and A. Splendore, “Über ‘Pébrine’ and verwandte Mikrosporidien,”Centrbl. Bakt. 1, 33, Orig. p. 150, 1903, and 36, Orig. p. 645, 2 pls., 1904; (29d) E.A. Minchin and H.B. Fantham, “Rhinosporidium kinealyi” (n.g., n.sp.),Q. J. Micr. Sci.49, p. 521, 2 pls., 1905; (30) A. Mrazek, “Über eine neue Sporozoenform” (Myxocystis),S. B. Böhm. Ges.8, 5 pp., 9 figs., 1897; (31)ib.“Glugea lophii,” Doflein,op. cit.10, 8 pp., 1 pl., 1899; (32) C. Perez, “Sur un organisme nouveau, Blastulidium,”C. R. soc. biol.55, p. 715, 5 figs., 1903; (33)ib.“Sur nouvelles Glugéidées,”op. cit.58, pp. 146-151, 1905; (34)ib.“Microsporidies parasites des crabes,”Bull. sta. biol. d’Arcachon, 8, 22 pp., 14 figs., 1905; (35) W.S. Perrin, “Pleistophora periplanetae,”Q. J. Micr. Sci.49, p. 615, 2 pls., 1906; (36) L. Plate, “Über einen einzelligen Zellparasiten” (Chitonicium),Fauna Chilensis, 2, pp. 601, pls., 1901; (37) M. Plehn, “Über die Drehkrankheit der Salmoniden” (Lentospora, n.g.),Arch. Protistenk. 5, p. 145, pl. 5, 1904; (37a) W.J. Ridewood and H.B. Fantham, “Neurosporidium cephalodisci, n.g., n.sp.,”Q. J. Micr. Sci.51, p. 81, pl. 7, 1907; (38) R. Sand, “Exosporidium marinum” (n.g.,n.sp.),Bull. soc. micr. belge, 24, p. 116, 1898; (39) T. Smith, “The production of sarcosporidiosis in the mouse,” &c.,J. Exp. Med.6, p. 1, 4 pls., 1901; (40) W. Stempell, “Über Thelohania mülleri,”Zool. Jahr. Anat.16, p. 235, pl. 25, 1902; (41)ib.“Über Polycaryum branchiopodianum” (n.g., n.sp.),Zool. Jahrb. Syst.15, p. 591, pl. 31, 1902; (42)ib.“Über Nosema anomalum,”Arch. Protistenk, 4, p. 1, pls. 1-3, 1904; (43) P. Thélohan, “Recherches sur les Myxosporidies,”Bull. sci. France belg.26, p. 100, 3 pls., 1895; (44) P. Vuillemin, “Le Sarcocystis tenella, parasite de l’homme,”C. R. ac. sci.134, p. 1152, 1902; (45) H.M. Woodcock, “On Myxosporidia in flat fish,”Proc. Liverp. Biol. Soc.18, p. 126, pl. 2, 1904; (46)ib.“On a remarkable parasite” (Lymphocystis),op. cit.p. 143, pl. 3, 1904.
Bibliography.—(For general works see underSporozoa.) (1) Bertram, “Beiträge zur Kenntnis der Sarcosporidien,”Zool. Jahrb. Anat.5, 1902; (2) L. Brasil, “Joyeuxella toxoides,” (n.g., n.sp.),Arch. zool. exp.N. et R. (3) 10, p. 5, 7 figs., 1902; (3) G.N. Calkins, “Lymphosporidium truttae,” (n.g., n.sp.),Zool. Anz. 23, p. 513, 6 figs., 1903; (3a)ib.The Life-History of Cytoryctes Variolae; Guarnieri, “Studies path. etiol. variola,”J. Med. Research(Boston, 1904), p. 136, 4 pls.; (3b) M. Caullery and A. Chappellier, “Anurosporidium pelseneeri, (n.g., n.sp.), Haplosporidie,” &c.,C. R. soc. biol.60, p. 325, 1906; (4) M. Caullery and F. Mesnil, “Sur un type nouveau” (Metchnikovella, n.g.),C. R. ac. sci.125, p. 787, 10 figs., 1897; (5)ib.“Sur trois Sporozoaires parasites de la Capitella,”C. R. soc. biol. 49, p. 1005, 1877; (6)ib.“Sur un Sporozoaire aberrant” (Siedleckia, n.g.),op. cit.50, p. 1093, 7 figs., 1898; (7)ib.“Sur le genre Aplosporidium” (nov.),op. cit.51, p. 789, 1899; (8)ib.“Sur les Aplosporidies,”C. R. ac. sci.129, p. 616, 1899; (9)ib.“Sur les parasites intimes des Annélides” (Siedleckia,Toxosporidium), C. R. ass. franç., 1899, p. 491, 1900; (10)ib.“Sur un type nouveau (Sphaeractinomyxon, n.g.) d’Actinomyxidies,”C. R. soc. biol.56, p. 408, 1904; (11)ib.“Phénomènes de sexualité dans le développement des Actinomyxidies,”op. cit.58, p. 889, 1905; (12)ib.“Recherches sur les Actinomyxidies,”Arch. Protistenk.6, p. 272, pl. 15, 1905; (13)ib.“Sur quelques nouvelles Haplosporidies d’Annélides,” C. R. soc. biol. 58, p. 580, 6 figs., 1905; (14)ib.“Sur des Haplosporidies parasites de poissons marins,”ib.p. 640, 1905; (15)ib.“Recherches sur les Haplosporidies,”Arch. zool. exp.(4) 4, p. 101, pls. 11-13, 1905; (16) L. Cohn, “Über die Myxosporidien von Esox lucius,”Zool. Jahr. Anat. 9, p. 227, 2 pls., 1896; (17)ib.“Zur Kenntniss der Myxosporidien,” Centrbl. Bakt. 1, Orig. 32, p. 628, 3 figs., 1902; (18)ib.“Protozoen als Parasiten in Rotatorien,” Zool. Anz. 25, p. 497, 1902; (19) F. Doflein, “Über Myxosporidien,” Zool. Jahr. Anat. 11, p. 281, 6 pls., 1898; (20)ib.“Fortschritte auf dem Gebiete der Myxosporidienkunde,”Zool. Centrbl. 7, p. 361, 1899; (21) R. Gurley, “The Myxosporidia,”Bull. U.S. Fish. Comm., 1892, p. 65, 47 pls., 1894; (22) E. Hesse, “Sur une nouvelle Microsporidie tétrasporée du genre Gurleya,”C. R. soc. biol.55, p. 495, 1903; (23)ib.“Thelohania légeri” (n.sp.),op. cit.57, pp. 570-572, 10 figs., 1904; (24)ib.“Sur Myxocystis Mrazeki Hesse,” &c., op. cit. 58, p. 12, 9 figs., 1905; (25) A. Laveran and F. Mesnil, “Sur la multiplication endogène des Myxosporidies,”op. cit.54, p. 469, 5 figs., 1902; (26)ib.“Sur la morphologie des Sarcosporidies,”op. cit.51, p. 245, 1899; (27)ib.“De la Sarcocystin,”op. cit.p. 311, 1899; (28) L. Léger, “Sur la sporulation du Triactinomyxon,”op. cit.56, p. 844, 4 figs., 1904; (29)ib.“Considérations sur ... les Actinomyxidies,”op. cit.p. 846, 1904; (29a) L. Léger and E. Hesse, “Sur une nouvelle Myxosporidie, Coccomyxa, n.g.,”C. R. ac. sci., 1st July 1907; (29b)ib.“Sur la structure de la paroisporale des Myxosporidies,”op. cit.142, p. 720, 1906; (29c) A. Lutz and A. Splendore, “Über ‘Pébrine’ and verwandte Mikrosporidien,”Centrbl. Bakt. 1, 33, Orig. p. 150, 1903, and 36, Orig. p. 645, 2 pls., 1904; (29d) E.A. Minchin and H.B. Fantham, “Rhinosporidium kinealyi” (n.g., n.sp.),Q. J. Micr. Sci.49, p. 521, 2 pls., 1905; (30) A. Mrazek, “Über eine neue Sporozoenform” (Myxocystis),S. B. Böhm. Ges.8, 5 pp., 9 figs., 1897; (31)ib.“Glugea lophii,” Doflein,op. cit.10, 8 pp., 1 pl., 1899; (32) C. Perez, “Sur un organisme nouveau, Blastulidium,”C. R. soc. biol.55, p. 715, 5 figs., 1903; (33)ib.“Sur nouvelles Glugéidées,”op. cit.58, pp. 146-151, 1905; (34)ib.“Microsporidies parasites des crabes,”Bull. sta. biol. d’Arcachon, 8, 22 pp., 14 figs., 1905; (35) W.S. Perrin, “Pleistophora periplanetae,”Q. J. Micr. Sci.49, p. 615, 2 pls., 1906; (36) L. Plate, “Über einen einzelligen Zellparasiten” (Chitonicium),Fauna Chilensis, 2, pp. 601, pls., 1901; (37) M. Plehn, “Über die Drehkrankheit der Salmoniden” (Lentospora, n.g.),Arch. Protistenk. 5, p. 145, pl. 5, 1904; (37a) W.J. Ridewood and H.B. Fantham, “Neurosporidium cephalodisci, n.g., n.sp.,”Q. J. Micr. Sci.51, p. 81, pl. 7, 1907; (38) R. Sand, “Exosporidium marinum” (n.g.,n.sp.),Bull. soc. micr. belge, 24, p. 116, 1898; (39) T. Smith, “The production of sarcosporidiosis in the mouse,” &c.,J. Exp. Med.6, p. 1, 4 pls., 1901; (40) W. Stempell, “Über Thelohania mülleri,”Zool. Jahr. Anat.16, p. 235, pl. 25, 1902; (41)ib.“Über Polycaryum branchiopodianum” (n.g., n.sp.),Zool. Jahrb. Syst.15, p. 591, pl. 31, 1902; (42)ib.“Über Nosema anomalum,”Arch. Protistenk, 4, p. 1, pls. 1-3, 1904; (43) P. Thélohan, “Recherches sur les Myxosporidies,”Bull. sci. France belg.26, p. 100, 3 pls., 1895; (44) P. Vuillemin, “Le Sarcocystis tenella, parasite de l’homme,”C. R. ac. sci.134, p. 1152, 1902; (45) H.M. Woodcock, “On Myxosporidia in flat fish,”Proc. Liverp. Biol. Soc.18, p. 126, pl. 2, 1904; (46)ib.“On a remarkable parasite” (Lymphocystis),op. cit.p. 143, pl. 3, 1904.
(H. M. Wo.)
ENDYMION,in Greek mythology, son of Aëthlius and king of Elis. He was loved by Selene, goddess of the moon, by whom he had fifty daughters, supposed to represent the fifty moons of the Olympian festal cycle. In other versions, Endymion was a beautiful youth, a shepherd or hunter whom Selene visited every night while he lay asleep in a cave on Mount Latmus in Caria (Pausanias v. 1; Ovid,Ars am.iii. 83). Zeus left him free to choose anything he might desire, and he chose an everlasting sleep, in which he might remain youthful for ever (Apollodorus i. 7). According to others, Endymion’s eternal sleep was a punishment inflicted by Zeus upon him because he ventured to fall in love with Hera, when he was admitted to the society of the Olympian gods (Schol. Theocritus iii. 49). The usual form of the legend, however, represents Endymion as having been put to sleep by Selene herself in order that she might enjoy his society undisturbed (Cicero,Tusc. disp.i. 38). Some see in Endymion the sun, setting opposite to the rising moon, the Latmian cave being the cave of forgetfulness, into which the sun plunges beneath the sea; others regard him as the personification of sleep or death (see Mayor on Juvenal x. 318).
ENERGETICS.The most fundamental result attained by the progress of physical science in the 19th century was the definite enunciation and development of the doctrine of energy, which is now paramount both in mechanics and in thermodynamics. For a discussion of the elementary ideas underlying this conception see the separate headingEnergy.
Ever since physical speculation began in the atomic theories of the Greeks, its main problem has been that of unravelling the nature of the underlying correlation which binds together the various natural agencies. But it is only in recent times that scientific investigation has definitely established that there is a quantitative relation of simple equivalence between them, whereby each is expressible in terms of heat or mechanical power; that there is a certain measurable quantity associated with each type of physical activity which is always numerically identical with a corresponding quantity belonging to the new type into which it is transformed, so that the energy, as it is called, is conserved in unaltered amount. The main obstacle in the way of an earlier recognition and development of this principle had been the doctrine of caloric, which was suggested by the principles and practice of calorimetry, and taught that heat is a substance that can be transferred from one body to another, but cannot be created or destroyed, though it may become latent. So long as this idea maintained itself, there was no possible compensation for the destruction of mechanical power by friction; it appeared that mechanical effect had there definitely been lost. The idea that heat is itself convertible into power, and is in fact energy of motion of the minute invisible parts of bodies, had been held by Newton and in a vaguer sense by Bacon, and indeed long before their time; but it dropped out of the ordinary creed of science in the following century. It held a place, like many other anticipations of subsequent discovery, in the system of Natural Philosophy of Thomas Young (1804); and the discrepancies attending current explanations on the caloric theory were insisted on, about the same time, by Count Rumford and Sir H. Davy. But it was not till the actual experiments of Joule verified the same exact equivalence between heat produced and mechanical energy destroyed, by whatever process that was accomplished, that the idea of caloric had to be definitely abandoned. Some time previously R. Mayer, physician, of Heilbronn, had founded a weighty theoretical argument on the production of mechanical power in the animal system from the food consumed; he had, moreover, even calculated the value of a unit of heat, in terms of its equivalent in power, from the data afforded by Regnault’s determinations of the specific heats of air at constant pressure and at constant volume, the former being the greater on Mayer’s hypothesis (of which his calculation in fact constituted the verification) solely on account of the power required for the work of expansion of the gas against the surrounding constant pressure. About the same time Helmholtz, in his early memoir on the Conservation of Energy, constructed a cumulative argument by tracing the ramifications of the principle of conservation of energy throughout the whole range of physical science.
Mechanical and Thermal Energy.—The amount of energy, defined in this sense by convertibility with mechanical work, which is contained in a material system, must be a function of its physical state and chemical constitution and of its temperature. The change in this amount, arising from a given transformation in the system, is usually measured by degrading the energy that leaves the system into heat; for it is always possible to do this, while the conversion of heat back again into other forms of energy is impossible without assistance, taking the form of compensating degradation elsewhere. We may adopt the provisional view which is the basis of abstract physics, that all these other forms of energy are in their essence mechanical, that is, arise from the motion or strain of material or ethereal media; then their distinction from heat will lie in the fact that these motions or strains are simply co-ordinated, so that they can be traced and controlled or manipulated in detail, while the thermal energy subsists in irregular motions of the molecules or smallest portions of matter, which we cannot trace on account of the bluntness of our sensual perceptions, but can only measure as regards total amount.
Historical: Abstract Dynamics.—Even in the case of a purely mechanical system, capable only of a finite number of definite types of disturbance, the principle of the conservation of energy is very far from giving a complete account of its motions; it forms only one among the equations that are required to determine their course. In its application to the kinetics of invariable systems, after the time of Newton, the principle was emphasized as fundamental by Leibnitz, was then improved and generalized by the Bernoullis and by Euler, and was ultimately expressed in its widest form by Lagrange. It is recorded by Helmholtz that it was largely his acquaintance in early years with the works of those mathematical physicists of the previous century, who had formulated and generalized the principle as a help towards the theoretical dynamics of complex systems of masses, that started him on the track of extending the principle throughout the whole range of natural phenomena. On the other hand, the ascertained validity of this extension to new types of phenomena, such as those of electrodynamics, now forms a main foundation of our belief in a mechanical basis for these sciences.
In the hands of Lagrange the mathematical expression for the manner in which the energy is connected with the geometrical constitution of the material system became a sufficient basis for a complete knowledge of its dynamical phenomena. So far as statics was concerned, this doctrine took its rise as far back as Galileo, who recognized in the simpler cases that the work expended in the steady driving of a frictionless mechanical system is equal to its output. The expression of this fact was generalized in a brief statement by Newton in thePrincipia, and more in detail by the Bernoullis, until, in the analytical guise of the so-called principle of “virtual velocities” or virtual work, it finally became the basis of Lagrange’s general formulation of dynamics. In its application to kinetics a purely physical principle, also indicated by Newton, but developed long after with masterly applications by d’Alembert, that the reactions of the infinitesimal parts of the system against the accelerations of their motions statically equilibrate the forces applied to the system as a whole, was required in order to form a sufficient basis, and one which Lagrange soon afterwards condensed into the single relation of Least Action. As a matter of history, however, the complete formulation of the subject of abstract dynamics actuallyarose (in 1758) from Lagrange’s precise demonstration of the principle of Least Action for a particle, and its immediate extension, on the basis of his new Calculus of Variations, to a system of connected particles such as might be taken as a representation of any material system; but here too the same physical as distinct from mechanical considerations come into play as in d’Alembert’s principle. (SeeDynamics:Analytical.)
It is in the cases of systems whose state is changing so slowly that reactions arising from changing motions can be neglected, that the conditions are by far the simplest. In such systems, whether stationary or in a state of steady motion, the energy depends on the configuration alone, and its mathematical expression can be determined from measurement of the work required for a sufficient number of simple transformations; once it is thus found, all the statical relations of the system are implicitly determined along with it, and the results of all other transformations can be predicted. The general development of such relations is conveniently classed as a separate branch of physics under the nameEnergetics, first invented by W.J.M. Rankine; but the essential limitations of this method have not always been observed. As regards statical change, the complete specification of a mechanical system is involved in its geometrical configuration and the function expressing its mechanical energy in terms thereof. Systems which have statical energy-functions of the same analytical form behave in corresponding ways, and can serve as models or representations of one another.
Extension to Thermal and Chemical Systems.—This dominant position of the principle of energy, in ordinary statical problems, has in recent times been extended to transformations involving change of physical state or chemical constitution as well as change of geometrical configuration. In this wider field we cannot assert that mechanical (or available) energy is never lost, for it may be degraded into thermal energy; but we can use the principle that on the other hand it can never spontaneously increase. If this were not so, cyclic processes might theoretically be arranged which would continue to supply mechanical power so long as energy of any kind remained in the system; whereas the irregular and uncontrollable character of the molecular motions and strains which constitute thermal energy, in combination with the vast number of the molecules, must place an effectual bar on their unlimited co-ordination. To establish a doctrine ofenergeticsthat shall form a sufficient foundation for a theory of the trend of chemical and physical change, we have, therefore, to impart precision to this motion of available energy.
Carnot’s Principle: Entropy.—The whole subject is involved in the new principle contributed to theoretical physics by Sadi Carnot in 1824, in which the far-reaching modern conception of cyclic processes was first scientifically developed. It was shown by Carnot, on the basis of certain axioms, whose theoretical foundations were subsequently corrected and strengthened by Clausius and Lord Kelvin, that a reversible mechanical process, working in a cycle by means of thermal transfers, which takes heat, say H1, into the material system at a given temperature T1, and delivers the part of it not utilized, say H2, at a lower given temperature T2, is more efficient, considered as a working engine, than any other such process, operating between the same two temperatures but not reversible, could be. This relation of inequality involves a definite law of equality, that the mechanical efficiencies of all reversible cyclic processes are the same, whatever be the nature of their operation or the material substances involved in them; that in fact the efficiency is a function solely of the two temperatures at which the cyclically working system takes in and gives out heat. These considerations constitute a fundamental general principle to which all possible slow reversible processes, so far as they concern matter in bulk, must conform in all their stages; its application is almost coextensive with the scope of general physics, the special kinetic theories in which inertia is involved, being excepted. (SeeThermodynamics.) If the working system is an ideal gas-engine, in which a perfect gas (known from experience to be a possible state of matter) is passed through the cycle, and if temperature is measured from the absolute zero by the expansion of this gas, then simple direct calculation on the basis of the laws of ideal gases shows that H1/T1= H2/T2; and as by the conservation of energy the work done is H1− H2, it follows that the efficiency, measured as the ratio of the work done to the supply of heat, is 1 − T2/T1. If we change the sign of H1and thus consider heat as positive when it is restored to the system as is H2, the fundamental equation becomes H1/T1+ H2/T2= 0; and as any complex reversible working system may be considered as compounded in various ways of chains of elementary systems of this type,whose effects are additive, the general proposition follows, that in any reversible complete cyclic change which involves the taking in of heat by the system of which the amount is δH, when its temperature ranges between Trand Tr+ δT, the equation ΣδHr/Tr-0 holds good. Moreover, if the changes are not reversible, the proportion of the heat supply that is utilized for mechanical work will be smaller, so that more heat will be restored to the system, and ΣδHr/Tror, as it may be expressed, ∫dH/T, must have a larger value, and must thus be positive. The first statement involves further, that for all reversible paths of change of the system from one state C to another state D, the value of ∫dH/T must be the same, because any one of these paths and any other one reversed would form a cycle; whereas for any irreversible path of change between the same states this integral must have a greater value (and so exceed the difference of entropies at the ends of the path). The definite quantity represented by this integral for a reversible path was introduced by Clausius in 1854 (also adumbrated by Kelvin’s investigations about the same time), and was named afterwards by him the increase of theentropyof the system in passing from the state C to the state D. This increase, being thus the same for the unlimited number of possible reversible paths involving independent variation of all its finite co-ordinates, along which the system can pass, can depend only on the terminal states. The entropy belonging to a given state is therefore a function of that state alone, irrespective of the manner in which it has been reached; and this is the justification of the assignment to it of a special name, connoting a property of the system depending on its actual condition and not on its previous history. Every reversible change in an isolated system thus maintains the entropy of that system unaltered; no possible spontaneous change can involve decrease of the entropy; while any defect of reversibility, arising from diffusion of matter or motion in the system, necessarily leads to increase of entropy. For a physical or chemical system only those changes are spontaneously possible which would lead to increase of the entropy; if the entropy is already a maximum for the given total energy, and so incapable of further continuous increase under the conditions imposed upon the system, there must be stable equilibrium.
This definite quantity belonging to a material system, its entropy φ, is thus concomitant with its energy E, which is also a definite function of its actual state by the law of conservation of energy; these, along with its temperature T, and the various co-ordinates expressing its geometrical configuration and its physical and chemical constitution, are the quantities with which the thermodynamics of the system deals. That branch of science develops the consequences involved in just two principles: (i.) that the energy of every isolated system is constant, and (ii.) that its entropy can never diminish; any complication that may be involved arises from complexity in the systems to which these two laws have to be applied.
The General Thermodynamic Equation.—When any physical or chemical system undergoes an infinitesimal change of state, we have δE = δH + δU, where δH is the energy that has been acquiredas heatfrom sources extraneous to the system during the change, and δU is the energy that has been imparted by reversible agencies such as mechanical or electric work. It is, however, not usually possible to discriminate permanently between heat acquired and work imparted, for (unless for isothermal transformations) neither δH nor δU is the exact differential of a function of the constitution of the system and so independent of its previous history, although their sum δE is such; but we can utilize the fact that δH is equal to Tδφ where δφ is such, as has just been seen. Thus E and φ represent properties of the system which, along withtemperature, pressure and other independent data specifying its constitution, must form the variables of an analytical exposition. We have, therefore, to substitute Tδφ for δH; also thechangeof internal energy is determined by the change of constitution, involving a differential relation of type
δU = −pδv + δW + μ1δm1+ μ2δm2+ ... + μnδmn,
when the system consists of an intimate mixture (solution) of masses m1, m2, ... mnof given constituents, which differ physically or chemically but may be partially transformable into each other by chemical or physical action during the changes under consideration, the whole being of volume v and under extraneous pressure p, while W is potential energy arising from physical forces such as those of gravity, capillarity, &c. The variables m1, m2, ... mnmay not be all independent; for example, if the system were chloride of ammonium gas existing along with its gaseous products of dissociation, hydrochloric acid and ammonia, only one of the three masses would be independently variable. The sufficient number of these variables (independent components) together with two other variables, which may be v and T, or v and φ, specifies and determines the state of the system, considered as matter in bulk, at each instant. It is usual to include δW in μ1δm1+ ...; in all cases where this is possible the single equation
δE = Tδφ − pδv + μ1δm1+ μ2δm2+ ... + μnδmn