Chapter XXI: Appendix: “Rhizopods in Poliomyelitis acuta.” (15)

The adult female _F. demarquayi_ measures from 65 to 80 mm. in length by 0·21 to 0·25 mm. in breadth. The head has a diameter of from 0·09 to 0·1 mm. The mouth is terminal. The genital pore opens at 0·76 mm. from the head. The alimentary canal is nearly straight and terminates in an anus, which is subterminal. The opening of the anus is marked by a slight papilla. The tail is curved. It rapidly diminishes in size just below the anal papilla. A characteristic pair of fleshy papillæ project from the tip of the tail. The diameter near the tip of the tail before its termination is 0·03 mm. _F. demarquayi_ is a thicker worm than _Ac. perstans_. It differs from _F. bancrofti_ in the greater size of the head, in the smaller tail, and particularly in the marked fleshy papillæ at the tip of the tail. These papillæ are knobby, and not simply cuticular as in _Ac. perstans_.

The male of _Filaria demarquayi_ has still to be found.

The adult female form of _F. demarquayi_ was found by Dr. Galgey in the body of a native of St. Lucia in whose blood the larvæ had been found during life. Five adult females were found in the connective tissue of the mesentery.

The larva measures 200 µ in length by 5 µ in breadth; it is sharp-tailed, and has no sheath. Its movements are very active, and the absence of a sheath enables it to glide along freely all over the slide. It observes no periodicity, being present in the peripheral circulation both by day and by night. As a rule, some eight or ten parasites are found in an ordinary preparation. Sometimes hundreds of these larval filariæ may be counted on every slide.

The intermediate host has not been discovered.

_Geographical Distribution._--St. Vincent, Dominica, Trinidad, and St. Lucia (West Indies), British Guiana, New Guinea (?).

*Filaria taniguchi*, Penel, 1905.

Female 68 by 0·2 mm. in breadth. Cuticle non-striated. Mouth two pairs of papillæ. Anus 23 mm. from extremity. Vulva 1·3 mm. from mouth. Larva 164 µ by 8 µ, sheathed. Tail truncated. Periodicity nocturnal.

_Habitat._--Lymphatic glands of man. Japan.

*Filaria (?) conjunctivæ*, Addario, 1885.

Syn.: _Filaria peritonei hominis_, Babes, 1880; _Filaria inermis_,
Grassi, 1887; _Filaria apapillocephata_, Condorelli-Francaviglia,
1892.

The female only of this species is known. It measures 16 to 20 cm. in length and 0·5 mm. in breadth, and is of a whitish or brownish tint. The cuticle is striated with fine transverse and more marked longitudinal striæ with the exception of a small field surrounding the mouth, which is terminal and has neither papillæ nor lips. The œsophagus measures 0·6 mm. in length. The anus is 3 mm. in front of the rounded posterior extremity, and behind it there are two (glandular?) sacs. The vulva is close behind the oral aperture; the vagina soon divides into two convoluted uteri, which are filled with eggs and embryos. Embryos 350 µ by 5·5 µ.

This species (115 mm. long) was first observed in Milan by Dubini
in the eye of a man; subsequently it was observed, encysted and
calcified (190 mm. long), by Babes in the gastro-splenic omentum of
a woman in Budapest, and finally one (95 mm. long) was extracted by
Vadela from a tumour the size of a pea in the ocular conjunctiva of a
woman in Catania (Sicily), which case has been described by Addario.
Possibly _Agamofilaria palpebralis_, Pace, 1867 (_nec_ Wilson, 1844),
and _A. oculi humani_, v. Nordm., 1832, are the same species.

_Filaria_ (?) _conjunctivæ_ is certainly only an incidental parasite of man; the horse and ass are its normal hosts, but it is not common in these animals, or is frequently confused with _Hamularia equi_, Gmelin, 1789.

Group. *Agamofilaria*, Stiles, 1906.

Not a generic but a group name for immature _Filariidæ_ the development of which does not admit of generic determination.

*Agamofilaria georgiana.*

Adult unknown, length from 32 to 53 mm. Maximum diameter 560 µ to 640 µ. Head no cephalic cone. Mouth small, circular, surrounded by six papillæ (two small latero-median and four sub-median). The larger papillæ are 24 µ from base to tip. Excretory pore about 0·5 mm. from head. Anus 64 µ to 128 µ from tip. Cuticle fine striæ near anus, occasionally elsewhere. Lateral lines clearly marked. Œsophagus 2·5 to 2·9 mm. Rectum 200 µ long.

_Habitat._--Superficial sores on the ankle of a negress, Georgia, U.S.A.

*Agamofilaria palpebralis*, Pace, 1867 (_nec_ Wilson, 1844).

100 by 1·5 mm., removed from a cyst in the left upper eyelid of a boy by Pace, in Palermo.

*Agamofilaria oculi humani*, v. Nordmann, 1832.

Syn.: _Filaria lentis_, Diesing, 1851.

The sexless Nematodes observed in the lens of the human eye were termed _Filaria oculi humani_. Only three cases are known. v. Nordmann observed very small round worms in the lens of a man and woman with cataract, and Gescheidt once found three specimens in the lens of a woman similarly affected.

The demonstration of nematode-like formations in the vitreous remains uncertain even when movements are observed, and when they cannot be extracted and examined microscopically the doubt may occur that one may have mistaken the remains of the hyaloid artery for a worm, which it resembles in form, size and colour; the slightest movement of the eye also causes it to move so that it simulates a living organism.

Accordingly it would be more correct to exclude all the cases known
only ophthalmoscopically (Quadri, 1857; Fano, 1868; Schoeler, 1875;
Eversbusch, 1891). There then remains only one positive case,
described by Kühnt in 1891. In this case it was possible to follow
the gradual growth of the parasite for some time, and the worm, which
measured only 0·38 mm. in length, was finally extracted.

*Agamofilaria labialis*, Pane, 1864.

The parasite measures 30 mm. in length; the anterior extremity is pointed; the terminal oral aperture is surrounded by four papillæ; the anus opens 0·5 mm. in front of the posterior extremity; the vulva is 2·5 mm. in front of the anus; the uterus is double; the anterior one passes with convolutions forward to the cephalic end; the posterior one is directed backwards and remains rudimentary.

Extracted from a small pustule on the inner surface of the upper lip.
Also found in Naples by Pierantoni in 1908.

The position of many of these worms is doubtful, and still more so is that of many other imperfectly described “Filariæ,” which are hardly more than useless and confusing names. These include the following:--

*Filaria (?) romanorum-orientalis*, Sarcani, 1888.

Observed in the blood of a Roumanian woman; 1 mm. in length, 0·03 mm. in breadth; tail end pointed, a tongue-like appendage on the head. Eggs the size of a red cell with developed embryo, apparently viviparous.

*Filaria (?) kilimaræ*, Kolb, 1898.

Several female specimens, 10 to 20 cm. long by 0·5 to 1 mm. broad, were once found free in the abdomen of a fallen Kitú warrior; according to Spengel, who examined them, the oral papillæ of these worms were similar to those of _Dracunculus medinensis_. Moreover, Kolb classifies together Nematodes that probably have no connection with each other.

*Filaria (?) sp.?*

Cholodkowsky calls attention to Filariæ that are still unknown which cause tumours resembling whitlows on the fingers of peasants of the Twer Government.

_Mikrofilaria powelli_, Penel, 1905. In Bombay.

_Mikrofilaria philippinensis_, Ashburn and Craig, 1906. In the Philippines.

Genus. *Setaria*, Viborg, 1795.

Syn.: _Hamularia_, Treutler, 1793; _Tentacularia_, Zeder, 1800 (_nec_
Bosc, 1797).

Mouth with projecting peribuccal armature deeply notched on the lateral margins, less so dorsally and ventrally. Tail in both sexes with peculiar caudal appendages.

Parasitic in serous cavities, especially of ruminants.

*Setaria equina*, Abildg., 1789.

Syn.: _Gordius equinus_, Abildg., 1789; _Filaria equi_, Gmelin, 1789;
_Hamularia lymphatica_, Treutler, 1793; _Tentacularia subcompressa_,
Zedder, 1800; _Filaria papillosa_, Rud., 1802; _Filaria hominis
bronchialis_, Rud., 1819; _Filaria hominis_, Dies., 1851; _Strongylus
bronchialis_, Cobb., 1879.

The body is whitish, filiform, pointed posteriorly. The cuticle presents a delicate transverse striation. The mouth is small, round, and surrounded by a chitinous ring, the border of which carries, at the sides, two semilunar lips, and there is on the dorsal as well as on the ventral surface a papilliform process; on the tail, corresponding with each sub-median line, is a conical papilla. The male measures 6 to 8 cm. in length; the posterior extremity ends in a corkscrew spiral; there are on each side four pairs of pre-anal and four or five post-anal papillæ; the spicules are unequal. The female measures 9 to 12 cm. in length and is viviparous; the embryos measure 0·28 mm. in length and 0·007 mm. in breadth.

_Setaria equina_ is a frequent parasite of horses and asses; it
inhabits the peritoneal cavity, and from there occasionally invades
the female genitalia or even the liver; it is found more rarely in
the pleural cavity or in the cranium. The statement that it also
occurs in the subcutaneous connective tissue is probably due to
confusion with _Setaria_ (_Filaria_) _hæmorrhagica_, Raill., 1885
(_Filaria multipapillosa_, Cond. et Drouilly, 1878). _Setaria labiata
papillosa_ (immature form) occurs in the eye of the horse, adults in
the peritoneal cavity.

Treutler, in 1790, found a filaria in the enlarged bronchial lymphatic gland of a patient suffering from phthisis. It measured 26 mm. in length and had two spicules, which Treutler mistook for mouth hooks, hence the name _Hamularia_. Blanchard mentions another case from Geneva, Brera a third and v. Linstow a fourth. As shown by the synonyms, a few authors consider this form to be a distinct species, which is hardly probable.

Genus. *Loa*, Stiles, 1905.

Characterized by the possession of cuticular bosses in both sexes (fig. 294).

*Loa loa*, Guyot, 1778.

Syn.: _Filaria oculi_, Gerv. et v. Ben., 1859; _Dracunculus
oculi_, Diesing, 1860; _Dracunculus loa_, Cobbold, 1864; _Filaria
subconjunctivalis_, Guyon, 1864.

The male measures 25 to 35 mm. in length, and 0·3 to 0·4 mm. in breadth; the cuticle is not striated, but, with the exception of the anterior and posterior extremities (1·5 mm.), is beset with numerous irregularly distributed bosses (4 µ to 12 µ high by 12 µ to 27 µ broad). The anterior extremity is somewhat attenuated, and in front is conical and transversely truncated. At the anterior limit of the conical part is a small papilla corresponding with the dorsal and ventral median lines, and a little in front six non-projecting sensory papillæ (two lateral, four sub-median). Excretory pore 0·65 mm. from the anterior end. The posterior extremity is attenuated and somewhat curved ventrally; the anus is 0·082 mm. distant from the rounded posterior border. In front of the anus on each side are three globular and pedunculated papillæ of different sizes, set close one behind the other but asymmetrically; behind the anus on either side are two smaller papillæ of a different shape; the anterior one resembles the pre-anal papillæ in form, but is smaller; the posterior one is conical, and rests with a broad base on the cuticle. The spicules are 0·113 and 0·176 mm. long.

The female measures 45 to 63 mm. in length by 0·5 mm. in breadth. It is also beset with irregularly distributed bosses, which in places lie close to each other, and extend to the anterior extremity; posteriorly they become less frequent, but are not entirely absent. The anterior extremity is conical, the posterior one straight, attenuated, rounded off, 0·17 mm. from the anus. The uteri contain eggs in the most various stages of development, as well as hatched-out larvæ, 253 µ to 262 µ in length and 4·7 µ to 5 µ in breadth. The vulva lies about 2 mm. from the head end. The vagina, 9 mm. long, divides into two branches, which at first run posteriorly and parallel to one another for about 18 mm. One then bends forward, runs as far as the œsophagus, bends here again and runs backward to end at the point of its first bending. The other branch at first runs straight backward and then bends forward, but before reaching the point of the first bend of the anterior tube bends backward again, forms again a loop and ends at the level of the anus. The tubes consist in the main of the uterus, then a club-shaped swelling, the receptaculum seminis, then the oviduct 2 mm. long, and finally the ovary.

Unsegmented eggs measure 32 µ by 17 µ, in the morula stage 40 µ by 25 µ, and when containing embryos 50 µ by 25 µ. The vitelline “shell” of the egg is, according to most authors, stretched by the embryo and becomes the sheath of the hatched larva. While still in the vulva, the larva measures 217 µ to 274 µ (average 246 µ) in fresh, 146 to 226 µ (average 192 µ) stained.

_Site of Worms._--In various localities; under the muscular aponeuroses on extensor surfaces of arms and legs, fingers, trunk, eyelid, conjunctiva, frænum linguæ, penis, pericardium, anterior chamber of eye, and, according to some authorities, in lymphatic vessels, _e.g._, those of spermatic cord. As many as thirty adults may be found. The worms appear to be frequently immature, and it has been stated that worms in superficial parts are immature, those situated deeply are mature, but the data are few.

The first accounts of _Loa loa_--long since forgotten--were reported
by Pigafetta, and are contained in a book of travels on the Congo
printed in 1598. In an accompanying illustration is depicted, not
only the ancient method of extraction of the Medina worm, but
also the operative removal of the filaria from the conjunctiva.
Subsequently the presence of the worm in negroes was confirmed by
Bajon in Guiana (1768) and by Mongin in Mariborou (San Domingo),
likewise in a negro (1770). At about this time a French ship’s
doctor, Guyot, was cruising on the West Coast of Africa; he observed
the parasite termed “loa” by the natives, and learned that it was
frequent in the negroes of the Congo district. Since that time
numerous observations have been reported. It was formerly common in
South America, where the parasite was imported by slaves, but it
disappeared when the traffic ceased; it was particularly prevalent
in the Congo, where it occurs not only in natives, but also in
Europeans. During recent times it has repeatedly been observed in
Europe in negroes as well as in white men who have lived on the West
Coast of Africa.

Nematodes of different size have been repeatedly observed in the eye of man, in the anterior chamber, lens and vitreous. For example, Mercier, in 1771 and 1774, removed a filaria out of the anterior chamber of two negroes in St. Domingo. One was 36 mm. long. Barkan, in 1876, in San Francisco, removed one from the eye of an Australian. Again, Cappez and Lacompte, in Brussels, in 1894, observed for some weeks immature Nematodes in the eye of a negro girl, aged 2-1/2 years, and then removed them. What these Nematodes actually were in these cases it is impossible to say.

_Structure of Larvæ._--In dried films the larva varies in size from 140·5 µ to 166·5 µ, average, 152·5 µ; while another set of measurements gave the values 131 µ, to 150 µ, average, 143·6. In films fixed with hot alcohol the dimensions were 208 µ to 254 µ, average, 231 µ.

The nerve ring 21·4 to 21·8 per cent. Excretory pore 30·4 to 31·8 per cent. Excretory cell 34·8 to 37·3 per cent. G1 cell 68·2 to 68·5 per cent. Anal pore 81·6 to 82·4 per cent. of total length. For other details _cf._ _Filaria bancrofti_.

_Larvæ in Blood._--These from their diurnal periodicity are known as _Mikrofilaria diurna_. The evidence that these larvæ are the young of the adult worm _Loa loa_ is: (1) They are identical in structure with larvæ taken from the uterus of _L. loa_; (2) their geographical distribution is the same as that of _L. loa_; (3) they eventually occur in the blood of patients suffering from Calabar swellings, a condition due to _L. loa_. Their occurrence in the blood in this latter condition and in _L. loa_ infections we shall consider later.

_Periodicity._--Here, as in the case of the larvæ of _Filaria bancrofti_, the larvæ that appear in the blood are probably the overflow simply of the larvæ which we assume, on analogy, to have their principal site in the lungs. They appear in the blood about the time of getting up, 6 to 8 a.m. (10 in 20 mm.^3), at 12 noon there are twenty-four, at 8 p.m. the number has fallen to eighteen, and at midnight to one, while from 2 a.m. to 6 a.m. none, or one only, may be found. This periodicity is, as a rule, a very constant one, but there are exceptions, and in certain cases more have been found at midnight than at 9 a.m. The periodicity is also lost in pathological conditions, _e.g._, sleeping sickness (_vide_ also under _Filaria bancrofti_). The possibility of non-periodic _Loa loa_ larvæ should also be considered.

_Pathology._--The parasite wanders about the body, and may be seen under the skin in thin parts. Their advance is in some cases at the rate of an inch in two minutes. During their progress they give rise to creeping sensations and to a condition of transient œdematous areas known as Calabar swellings on various parts of the body, _e.g._, arm. These vary in diameter from 1 to 10 cm., and often shift their position an inch or so a day. They give rise to a certain amount of redness, tension and heat, and their development is promoted by muscular action of the part. They disappear to reappear elsewhere. The condition is associated with a high eosinophilia, 50 per cent. being not uncommon. Patients known to harbour _L. loa_, _e.g._, native children, frequently show no larvæ in their blood, but they may do so after years of infection. Again, in patients having an infection of _Mikrofilaria diurna_, there is frequently at the time no evidence of the presence of _Loa loa_ adults. Here again they may appear later, but the conditions which determine whether persons infected with _L. loa_ show larvæ in the blood, or persons infected with _Mikrofilaria diurna_ also show _L. loa_, are unknown, though explanations unsupported by facts abound. Likewise also the mode of production of the swellings is unknown.

Not uncommonly _Mikrofilaria perstans_ occurs in the blood together with _M. diurna_.

_Duration of Life._--This is long, as some cases have been observed five to six years after leaving Africa. The incubation period is about a year.

_Life-history._--Development of the larvæ takes place in the salivary glands of Chrysops sp. as shown by Leiper.

_Geographical Distribution._-- West Africa, especially in Congo.

Genus. *Acanthocheilonema*, Cobbold, 1870.

Cuticle striated _longitudinally_. Œsophagus divided into two portions. Tail in both sexes with short lateral conical cuticular appendages. Spicules unequal, the larger membranous distally, the smaller hooked. Vulva in œsophageal region.

*Acanthocheilonema perstans*, Manson, 1891.

Syn.: _Filaria perstans_, P. Manson, 1891; _Filaria sanguinis
hominis_ var. _minor_, Manson, 1891.

The adult female _Ac. perstans_ measures 70 to 80 mm. in length by 120 µ to 140 µ in breadth. The head is club-shaped and measures 0·07 mm. in diameter. The vulva opens at 0·6 to 1·0 mm. from the head. The tail is curved and presents a cuticular thickening which forms two triangular appendages. The anus opens at the apex of a papilla situated in the concavity of the curve formed by the tail 150 µ from the end. The diameter of the tail just before termination is 0·02 mm.

The adult male measures 45 mm. in length by 60 µ to 80 µ in breadth. The diameter of the head is 0·04 mm. The tail is much curved. There are four pairs of pre-anal papillæ and two pairs of post-anal papillæ. Spicules very unequal in size. Cloaca 121 µ from the tail end. At the tail end two triangular cuticular appendages.

The adult worms inhabit the connective tissue at the base of the mesentery, especially in the region of the pancreas, abdominal aorta and suprarenals. To find them the mesentery should be removed, placed in a 2 per cent. solution of formalin, and then carefully examined at leisure.

_Mikrofilaria perstans._--160 µ to 210 µ by 5 µ to 6 µ broad. Has no sheath. Cuticle transversely striated. Tail rounded off, not pointed. Nerve ring at 34 µ. Excretory pore 49 µ, genital pore 125 µ from head. Smaller larvæ 90 µ to 110 µ by 4 µ broad. A “fang” is also described on the head.

_Mf. perstans._ _Mf. demarquayi._
(1) Tail stumpy. (1) Tail pointed.
(2) Column of nuclei extends to (2) Does not extend to tip.
tip of tail.

_Periodicity._--None.

_Life-history._--Unknown.

_Geographical Distribution._--Very common in many parts of Africa: Sierra Leone, Dahomey, Northern Nigeria, Southern Nigeria, Cameroons, Ivory Coast, Gold Coast, Old Calabar, Congo, Uganda. Absent from Zululand, Basutoland. On the East Coast of Africa it is not found in the towns of Zanzibar and Mombasa, neither is it found in the country of the Masi, nor amongst the Kavirondo, who dwell along the north-east shores of Lake Victoria.

In South America, _Ac. perstans_ is very common amongst the aboriginal Indians in the interior of British Guiana. However, it is not found in Georgetown and in New Amsterdam, neither is it found in the cultivated strip of coast lying between these two towns, but it is common on the coast farther north near the Venezuelan boundary, where the forests stretch to the sea. The Waran Indians, who live at the mouth of the Waini river, harbour this parasite. It is absent in the West Indies.

Topographically, _Ac. perstans_ is found only in areas covered by dense forest growth and abounding in swamps. In Kavirondo, where the forest disappears and the land is covered with scrub and short grass, it is not found; likewise it is not found on the grassy plains of the highlands of British East Africa. Towns and cultivated areas are free from it.

Genus. *Dirofilaria.* Railliet and Henry, 1911.

Body very long, thread-like, cuticle transversely striated. Mouth with six papillæ. Male tail spiral with voluminous pre-anal and some large post-anal papillæ; spicules unequal. Vulva near the anterior hundredth of body; viviparous. Parasitic in heart or blood-vessels and subcutaneous tissue.

*Dirofilaria magalhãesi*, R. Blanchard, 1895.

Syn.: _Filaria bancrofti_, v. Linstow, 1892; _Filaria bancrofti_,
P. S. de Magalhães, 1892 (_nec_ Cobbold, 1877).

The male measures 83 mm. in length by 0·28 to 0·40 mm. in breadth. The anterior extremity is rounded, and has no papillæ (?6); the posterior extremity exhibits a double curve, with four pre-anal and four post-anal papillæ on each side. These are large and have a villous appearance. The mouth is round and unarmed, the pharynx measures 1 mm. in length, is cylindrical, very muscular, and its hinder part is dilated. The anus is situated 0·11 mm. in front of the hind end. There are probably two unequal spicules; one only, however, is known--apparently the shorter one--the length of which is given as 0·17 to 0·23 mm.

The female measures 155 mm. in length and 0·6 to 0·8 mm. in breadth; the rings of the cuticle are 0·005 mm. apart (in the male 0·003 mm. apart); the anterior extremity is slightly thickened and club-like, the posterior extremity is slender, and terminates obtusely; the lateral line is 0·127 mm. in breadth (that of the male 0·007 to 0·008 mm.); the anus opens 0·13 mm. in front of the hind end, the vulva is 2·5 mm. distant from the mouth, the ovaries are two much convoluted tubes. The eggs measure 38 µ by 11 µ.

This species was first discovered at a _post-mortem_, in the left
ventricle, by J. P. Figueira de Saboia in Rio de Janeiro, and has
been described by P. S. de Magalhães.

_D. immitis_ occurs in the right ventricle of the heart of the dog in
Europe and the Tropics.

_D. repens_ is also a common subcutaneous Nematode in dogs in Annam.

Sub-family. *Onchocercinæ*, Leiper, 1911.

Cuticle with spiral thickenings.

Genus. *Onchocerca*, Diesing, 1841.

Male with four pre-anal papillæ. Female with vulva situated anteriorly.

*Onchocerca volvulus*, R. Leuckart, 1893.

Syn.: _Filaria volvulus_, R. Leuckart, 1893.

The adult male measures 30 to 35 mm. in length by 0·14 mm. in breadth. The body is white, filiform, attenuated at both ends. The head is rounded and has a diameter of 0·048 mm. The cuticle is distinctly transversely striated. The mouth is unarmed. The alimentary canal is straight, the anus opening 0·07 mm. from the tip of the tail. The tail is strongly curved and somewhat flattened on the concave surface. There are three papillæ, one large and two small, on each side of the cloaca and one large and two post-anal small papillæ. Two curved spicules, 0·166 and 0·08 mm. respectively.

The adult female is of uncertain length, but much longer than the male, probably about 10 to 12 cm. The head is rounded and truncated; it measures 0·065 mm. in diameter. The tail is curved. The vulva opens 0·55 mm. from the head. The hand-like cuticular thickenings are well marked. Eggs ovoid with a prolongation at each pole “like an orange wrapped in tissue paper.” The larva measures about 300 µ by 7 µ to 8 µ; it has no “sheath.” The body tapers from about the last fifth of its length, and terminates in a sharply pointed tail. At about the anterior fifth of the body there is a *V* spot.

_O. volvulus_ is found in peculiar subcutaneous tumours, the size of a pea to that of a pigeon’s egg. The same patient may present one or several of these tumours. The regions of the body most frequently affected are those in which the peripheral lymphatics converge. Thus they are usually found in the axilla, in the popliteal space, about the elbow, in the sub-occipital region and in the intercostal spaces. The tumours are never adherent to the surrounding structures, and can be easily enucleated. They are formed of a dense connective tissue wall and internally a looser fibrous meshwork. This is traversed by a series of canals in which the worms lie, but they are also partly embedded in the denser wall. The canals apparently dilate into cavities filled with slimy pus-like fluid consisting largely of larvæ. According to Brumpt the posterior extremity of the male, and the anterior extremity of the female with its vaginal opening, are free in one of the spaces for the purpose of copulation and parturition. If a tumour be cut into and placed in salt solution, Rodenwaldt states that the undamaged males wander out into the solution.

The formation of the tumours is elucidated by Labadie-Lagrave and Deguy’s case. The authors found an immature female _Onchocerca volvulus_ in a lymphatic vessel partly obstructed by an infiltration of fibrin and leucocytes. It appears, therefore, that the presence of the parasites within the lymphatics gives rise to an inflammatory process, and that the consequent fibrinous deposit envelops the parasites, obliterates the lumen of the vessel, and ultimately isolates the affected tract. At any rate, in young tumours the worms appear to lie in a structureless substance permeated by leucocytes in which connective tissue is gradually organized from the periphery, thus isolating the worms.

In cases of infection with _O. volvulus_ larvæ have been found by Ouizilleau, Fülleborn, and Simon in lymph glands, and in the finger blood if considerable pressure is used so as to squeeze lymph out of the tissues. They are _sheathless_, and the following are the dimensions in ordinary dried films: Length, 274 µ; nerve ring, 23·7 per cent.; G1 cell, 69·6 per cent.; end of last tail cell, 96·3 per cent. The dimensions of larvæ of _O. volvulus_ taken from the uterus and prepared in the same way are: Length, 224·5 µ; nerve ring, 24·3 per cent.; G1 cell, 68·9 per cent.; end of the last tail cell, 95·5 per cent. In all probability the larvæ in the glands and blood are those of _O. volvulus_.

According to the natives, the tumours may last indefinitely and never ulcerate. Some old patients told Brumpt that their tumours had been present since childhood. Probably _Onchocerca volvulus_, like some other _Filariidæ_, may live for many years.

_O. volvulus_ occurs in various parts of West Africa: Gold Coast, Sierra Leone, Dahomey, Lagos, Cameroons. Brumpt, on the banks of the Welle between Dongon and M’Binia (Belgian Congo), found about 5 per cent. of the riverine population affected.

Family. *Trichinellidæ*, Stiles and Crane, 1910.

Sub-family. *Trichurinæ*, Ransom, 1911.

Male with a single long spicule, with sleeve-like sheath. One ovary. Eggs with an opening at each pole closed by a plug-like operculum. Eggs hatch on being swallowed by a new host. Genera: Trichuris, Capillaria.

Genus. *Trichuris*, Röderer and Wagler, 1761.

Syn.: _Trichocephalus_, Goeze, 1782 (_nec Trichiurus_, L., 1758);
_Mastigodes_, Zeder, 1803.

The anterior part of the body is very long and thread-like; the
posterior, much shorter part, is thicker, rounded posteriorly, and
the anus is terminal. The males have the posterior extremity spirally
rolled; the vulva is situated at the commencement of the posterior
part of the body. The Trichocephali live in the large intestine of
mammals, the cæcum by predilection; their development is direct,
infection occurs through the ingestion of embryo-containing eggs.

*Trichuris trichiura*, Linnæus, 1761.

Syn.: _Trichocephalus trichiurus_, L., 1771; _Ascaris trichiura_,
L., 1771; _Trichocephalus hominis_, Schrank, 1788; _Trichocephalus
dispar_, Rud., 1801.

The male measures 40 to 45 mm. in length, the spicule is 2·5 mm. long, its retractile sheath is beset with spines. The female measures 45 to 50 mm. in length, of which two-fifths appertain to the posterior part of the body. The ova are barrel-shaped and have a thick brownish shell which is perforated at the poles. Each opening is closed by a light-coloured plug. The eggs measure 50 µ to 54 µ in length and 23 µ in breadth; they are deposited before segmentation. _Trichuris trichiura_ usually lives in the cæcum of man, and is also occasionally found in the vermiform appendix and in the colon, exceptionally also in the small intestine; usually only a few specimens are present, and these do not cause any particular disturbance, although, as Askanazy found, they feed on blood; in other cases cerebral symptoms of more or less severity are observed when Trichocephali are present in large numbers. At _post-mortems_ performed soon after death the filiform anterior extremity of the worm is frequently found embedded in the mucous membrane (Askanazy).

The whip worm is one of the most common parasites of man and
appears to be distributed over the entire surface of the globe; it
is, however, more frequent in the warmer regions. It is found in
persons of both sexes and all ages with the exception of infants. In
autopsies it is found in the following numbers: In Dresden in 2·5 per
cent., in Erlangen in 11·1 per cent., in Kiel in 31·8 per cent., in
Munich in 9·3 per cent., in Petrograd in 0·18 per cent., in Göttingen
in 46·1 per cent., in Basle in 23·7 per cent., in Greenwich in 68 per
cent., in Dublin in 89 per cent., in Paris in about 50 per cent.,
and in Southern Italy in almost 100 per cent. On examining the fæces
the eggs of the whip worm were found as follows: In Munich in 8·26
per cent., in Kiel in 45·2 per cent., in Greifswald in 45 per cent.,
in North Holland in 7 per cent., in Novgorod in 26·4 per cent., in
Petrograd in 5 per cent., in Moscow in 5·3 per cent.

The development of the eggs is completed in water or in moist soil, and occupies a longer or shorter time according to the season; the eggs possess great powers of resistance, as do the larvæ, which, according to Davaine, may remain as long as five years in the eggshell without losing their vitality. Leuckart proved by experiment that direct infection with _Trichuris ovis_ (_Ovis aries_) and _T. crenata_ (_Sus scrofa dom._) was produced by embryo-containing eggs; Railliet obtained the same results with _T. depressiuscula_ of dogs, and Grassi subsequently, by means of two experiments, demonstrated the direct development of _Trichuris trichiura_. In one case embryo-containing eggs were swallowed on June 27, 1884, and on July 24 the ova of Trichocephali were found in the fæces for the first time.

_Trichuris trichiura_ is found not only in man, but also in various monkeys (_T. palæformis_, Rud.), as well as in lemurs (_T. lemuris_, Rud.).

Other species are _T. crenata_ in pig; _T. ovis_ in cattle, sheep, goat, and pig (?); _T. depressiuscula_ in dog; _T. campanula_ in cat; _T. unguiculata_ in rabbit and hare; _T. cameli_ in camel; _T. discolor_ in humped cattle; _T. nodosus_ in mouse; _T. alcocki_ in the thamin (India); _T. globulosa_ in camel; _T. giraffæ_ in giraffe.

Sub-family. *Trichinellinæ*, Ransom, 1911.

Male without spicule; females ovoviviparous. Larvæ penetrate muscles of host and become encysted. Genus: Trichinella.

Genus. *Trichinella*, Railliet, 1895.

Syn.: _Trichina_, Owen, 1835 (_nec_ Meigen, 1830).

Very small _Trichinellinæ_, the males of which have two conical
appendages at the caudal extremity; the vulva is situated at the
border of the anterior fifth of the body. There is only one species.

*Trichinella spiralis*, Owen, 1835.

Syn.: _Trichina spiralis_, Owen, 1835.

The male measures 1·4 to 1·6 mm. in length and 0·04 mm. in diameter. The anterior part of the body is narrowed, the orifice of the cloaca is terminal and lies between the two caudal appendages; internal to these are two pairs of papillæ, dorsal one behind the other. The cloaca is evertible for copulation. The females measure 3 to 4 mm. in length and 0·06 mm. in diameter; anus terminal.

_Trichinella spiralis_ in its adult stage inhabits the small intestine of man, pig, wild boar, rat. The young do not leave the body of the host but become encysted in the muscles. Experimentally it develops in the black rat (_Mus rattus_), the sewer rat (_M. decumanus_), the domestic pig (_Sus scrofa dom._), the wild boar (_Sus scrofa ferox_), the domestic dog (_Canis familiaris_), the fox (_C. vulpes_) the badger (_Meles taxus_), the polecat (_Putorius fœtidus_), the marten (_Mustela foina_), the raccoon (_Procyon lotor_), the hippopotamus and the cat, and many other mammals (rodents and carnivora); Trichinellæ have been artificially introduced, by administering the encysted stage, into the dog, the mole (_Talpa europæa_), the mouse (_Mus musculus_), the hare (_Lepus timidus_), the rabbit (_L. cuniculus_), the hedgehog (_Erinaceus europæus_), the marmot (_Cricetus vulgaris_), the vole, the dormouse, the sheep, the calf, the horse, etc. Human beings and the pig, rat, mouse, guinea-pig and rabbit are most easily infected; less easily the sheep, calf and horse; with difficulty the cat, dog and badger. Trichinella can also be reared in birds (fowl, pigeon and duck), but the young do not encyst in the muscular system, but are expelled with the fæces. By cold-blooded animals as well as by insects (_Calliphora vomitaria_), encysted Trichinellæ are evacuated without undergoing any change, but they will still develop if subsequently ingested, say, by rabbits. According to Gujon, however, Trichinella can develop in salamanders, because he has found Trichinella of the muscles in these animals after they had been fed on encysted specimens. A high temperature (30°C.) must be provided in which to keep the experimental animals to ensure the success of the infection.

_History._--Encapsuled Trichinellæ had been observed in London by
Peacock (1828) and by J. Hilton (1833) in the muscular system of man;
soon after (1835), Paget found them in London in an Italian who had
died of tuberculosis, and recognized them to be encysted entozoa,
which R. Owen described as _Trichina spiralis_. Soon after, some
further observations were reported on the occurrence of encysted
Trichinellæ, in man, in England, Berlin, Heidelberg, Denmark, North
America; they were also found in the pig (Leidy, Philadelphia)
and the cat (Herbst, Göttingen, and Gurlt, Berlin). Herbst even
succeeded in infecting a badger with encysted Trichinellæ, and
subsequently infected two dogs with the flesh of this badger (1850).
In 1855 R. Leuckart (Giessen) also commenced feeding experiments,
and, like Küchenmeister and Virchow (1859), first went on the wrong
track because it was believed at that time that Trichinellæ were
the larvæ either of Trichocephalus or Strongylus. Nevertheless,
these experiments yielded some important results; they showed that
Trichinellæ become adult in the intestine within a few days, and that
the females are viviparous (Leuckart). Until that time Trichinellæ
had been regarded as fairly harmless guests of man, but opinions
soon changed when Zenker in Dresden (January, 1860), in performing
the autopsy of a girl, aged 10, who had entered the hospital with
typhoid symptoms and there died, found Trichinellæ (not yet encysted)
in the muscles; the intestinal lesions characteristic of typhoid
were lacking, but numerous adult Trichinellæ were found in the
intestine. Inquiries elicited the fact that at about Christmas time
the girl had been taken ill after eating pork, and at the same time
the butcher from whom the meat was bought as well as several of his
customers fell sick: the pickled pieces of the same meat were full
of Trichinellæ. In the face of this information it was not difficult
to ascertain the cause of the disease and the manner of infection
in Zenker’s case, and it was not long before Leuckart, Virchow and
Zenker were able by renewed experiments to demonstrate the cycle
of development of _Trichinella spiralis_. Similar investigations
followed by Claus in Würzburg, Davaine in Paris, Fuchs and
Pagenstecher in Heidelberg, etc.

Hardly had Zenker’s case been published than numerous observations on
trichinosis in man appeared, some referring to isolated cases, others
to small or great epidemics, and nearly all from North Germany.
The worst epidemic was that of Hadersleben (1865), in which place,
numbering hardly 2,000 inhabitants, 337 persons were taken ill within
a short time, and of these 101 died. The source of infection proved
to be a single pig, the flesh of which had been mixed with that of
three other pigs; 200 of the badly infected persons had exclusively
eaten raw pork.

Moreover, it soon became clear that epidemics of trichinosis had been
observed in Germany prior to 1860, but that their nature had not been
recognized, although in a few cases Trichinellæ had been found in the
muscles of those who had succumbed.

HISTORY OF THE DEVELOPMENT OF _Trichinella spiralis_.

Shortly after their introduction into the intestine of experimental animals the encysted Trichinellæ escape from their capsules, which are destroyed by the gastric juices, and they then enter the duodenum and jejunum, where they become adult. During this period they do not grow much, the males from 0·8 to 1·0 to 1·2 to 1·5 mm.; the females to 1·5 to 1·8 mm. Soon after copulation, which takes place in the course of two days, the males die; the females, which during the following days attain a length of 3 to 3·5 mm., either bore more or less deeply into the villi or, by means of Lieberkühn’s glands, into the mucous membrane (Askanazy, Cerfontaine, Geisse), and thus usually attain the lymph spaces. A few also pierce the intestinal wall and are then found in the mesentery and glands. The females deposit their young, the number of which, according to Leuckart, averages at least 1,500, in the lymph spaces; the newly born larvæ measure 90 µ to 100 µ in length, 6 µ in diameter, and they do not appear to increase in size during their migrations. The migrations are mostly passive, that is to say, the larvæ are carried along mainly by the lymph stream to the heart, but sometimes they are active, as may be inferred from the fact that young Trichinellæ are found in various parts of the intestinal wall beyond the chyle and lymph spaces, as well as in abundance in the abdominal cavity. Trichinellæ occur in the heart’s blood of artificially infected animals seven to twenty-three days after infection. If scanty, dilute the blood with about ten times the amount of 3 per cent. acetic acid and centrifugalize.

The young brood is distributed from the heart throughout the entire body, but the conditions necessary to its further development are found only in striated muscle; the young Nematodes penetrate the capillaries, attain the intramuscular connective tissue and then invade the fibres (Virchow, Leuckart, Graham[304]). On the ninth or tenth day after infection the first Trichinellæ have reached their destination; but further invasions are constantly taking place because the intestinal Trichinellæ live from five to seven weeks, and continue to produce their young.

[304] Trichinellæ that are unable to penetrate into muscular fibres invariably die, no matter where else they settle; their occurrence in the adipose tissue is disputed, but is still possibly correct, as bundles of muscles are present in the fat of bacon. The Trichinellæ do not settle in heart muscle, although they may reach it in cases of heavy infection; they then die or wander into the pericardium, and eventually into the heart cavities.

_Symptoms._--(1) Period of invasion: Gastro-intestinal symptoms--nausea, vomiting, watery diarrhœa, colic. Muscular pains may occur even at this period. Recurrent abdominal pains about the eighth day, a _temporary_ œdema. Embryos are abundant in the serous cavities.

(2) Period of dissemination: Second week. Myositis, variable in amount, is the predominant symptom. The biceps and calf may be hard and tender. Mastication, speech, respiration, etc., may be difficult and painful. Dyspnœa may be intense. Temperature 104° to 105° F.

(3) Period of encystment: Symptoms of marked cachexia. Third week: Second period of œdema, especially of face. Delirium, somnolence, lung affections. Death or gradual subsidence of symptoms in mild cases.

Eosinophilia (50 per cent. or more) is present.

In consequence of the new batches of young produced during several
weeks, the above-mentioned symptoms of disease are often considerably
aggravated; the fever increases, delirium may arise, and infiltration
of the lungs, fatty degeneration of the liver and inflammation of the
kidneys may ensue; the initial slight œdema may extend, the strength
dwindles, and in many cases the patients succumb to the trichinosis.
In severe cases improvement of the condition is only apt to occur in
the fourth or fifth week; the convalescence is always protracted.

The muscular fibres attacked degenerate, the transverse striation at first disappearing; the fibres then assume a granular appearance, the nuclei multiply and become enlarged, and are surrounded by an area of granular material, which stains more deeply than the remaining contents of the sarcolemma. Two or three weeks after infection, the spirally rolled-up Trichinellæ have grown to 0·8 to 1·0 mm., and in their vicinity the muscular fibre is swollen, spindle-shaped, and the sarcolemma is glassy and thickened. The inflammation also extends to contiguous fibres, especially to the intramuscular tissue, which proliferates greatly, especially in the vicinity of the degenerated fibres. While the latter become more and more absorbed, the capsule is formed by the inflamed connective tissue, which, penetrating into the glassy and thickened sarcolemma from the poles of the spindle, forms the cystic membrane. According to other authorities, the larvæ settle in the _inter_muscular connective tissue which forms the cyst and not in the muscular fibres within the sarcolemma. The cysts are lemon-shaped and usually lie with their longitudinal axis in the direction of the muscular fibres; on an average they measure 400 µ in length by 250 µ in breadth.

Later on fat cells appear at their poles, and after about six or nine months they commence to calcify, the process starting at the poles (fig. 305). Finally, sometimes after the lapse of years, the captive Trichinellæ themselves become calcified.

According to experience, Trichinellæ are not evenly distributed in the muscular system of pigs; the diaphragm, the muscles of the larynx, tongue, abdomen and intercostal spaces are their favourite positions; this predilection for the respiratory muscles is explained by their regular contractions, owing to which regular narrowings of the capillaries take place, thus favouring the settling of the circulating Trichinellæ. The same circumstance probably explains the frequency of the parasites in the tongue.

Possibly also the Trichinellæ that bore direct through the intestine may, from the abdominal cavity, penetrate the muscles in the vicinity. Frequently also encysted Trichinellæ are found in remarkable numbers in the vicinity of the points of insertion of the tendons, this proclivity being probably connected with the fact that the Trichinellæ first of all wander into the muscular fibres and find a natural barrier at the points of insertion of the tendons.

The Trichinellæ, in their encysted condition, may remain alive and capable of development for many years--in the pig eleven years and in man as much as twenty-five to thirty-one years. Encystment, however, is not a necessary condition for the development of the brood, that is to say, Trichinellæ which reach the gut of suitable animals become sexually mature and multiply provided that they have developed so far as to possess a rudimentary genital spot, which occurs when the body is 0·5 to 0·75 mm. long, but all the same a great part of non-encapsuled Trichinæ perish on their passage through the stomach.

The black rat (_Mus rattus_), and more particularly the sewer rat (_Mus decumanus_[305]), are the normal hosts of _Trichinella spiralis_. These animals, especially the last-named species, infect themselves very easily, as they are cannibalistic, and they also transmit trichinosis to other species by which they are devoured, such as pigs, dogs, cats, foxes, bears and martens. Rats are infected also by the ingestion of fæcal matter from infected animals which contains trichinæ (Höyberg). Man becomes infected with Trichinella by eating the flesh, insufficiently cooked, of infected pigs, also, but more rarely, by eating the infected flesh of wild boars, dogs, cats, bears and foxes.

[305] It is still a matter of dispute and can hardly be definitely settled whether Trichinellæ were brought to Europe by the sewer rats which invaded Europe at the end of the eighteenth century, or whether they were imported with the Chinese pig in 1820 or 1830, when it was introduced into England and Germany to cross with the native breeds, or whether finally Trichinellæ are also indigenous to Europe.

The infection of pigs may likewise take place by their having access
to the offal of trichinous pigs, or being actually fed on it. These
are, however, exceptions, which, as a matter of course, are of great
importance in certain places. As a matter of fact, the rats examined
for Trichinella were always found to be severely infected. Thus
Billings, in the knackers’ yard at Boston, found that 76 per cent.
of the rats were infected, and in an export slaughterhouse 100 per
cent. were found to harbour the parasite; in the city of Boston 10
per cent. of the rats had trichinosis. Heller found that of 704 rats,
from twenty-nine different places in Saxony, Bavaria, Würtemberg and
Austria, 8·3 per cent. were infected with Trichinellæ; of the rats
caught in the knackers’ yards, 22·1 were diseased; of those taken in
slaughterhouses, 2·3 were infected, and of rats from other localities
only 0·3 per cent. harboured the parasite. Leisering found almost the
same figures, but in rats from slaughterhouses 5·3 per cent. were
infected.

The geographical distribution of _T. spiralis_ does not correspond with the occurrence of trichinosis in man; local customs are an important factor; for instance, the custom of eating pork in a condition that does not affect the life of the enclosed trichinella. In places where such customs do not prevail, epidemics do not occur--at the most there are isolated cases of the disease, although there be a great number of infected pigs. The following conditions prevail in North America: In Boston, Billings found that 4 to 5·7 per cent. of the pigs examined were trichinous; Belfield and Atwood found that 8 per cent. were infected in Chicago; Salmon found on an average that 2·7 per cent. were infected (but at various places the percentage fluctuated between 0·28 to 16·3 per cent.), yet epidemics of trichinosis hardly ever occur in North America, and only isolated cases of the disease are met with in German immigrants, who keep to their native customs.

This report, according to the researches of H. U. Williams, must be
considerably modified. This author has examined the muscular system
of human cadavers according to the method employed by inspectors of
meat for pigs. The investigations were conducted in the Pathological
Institute of the University of Buffalo, and the observer has examined
505 bodies since 1894, of which 27 (= 5·34 per cent.) were invaded by
Trichinella. The cases, according to the nationality, are divided as
follows:--

---------------------+----------+--------+---------+-------------
| | Trichinella | Percentage
| Examined +--------+---------+ of positive
| | Absent | Present | results
---------------------+----------+--------+---------+-------------
Americans: | | | |
(_a_) Whites | 207 | 201 | 6 | 2·89
(_b_) Negroes | 70 | 65 | 5 | 7·14
British and Irish | 62 | 57 | 5 | 8·06
Canadians | 12 | 10 | 2 | 16·66
Germans | 49 | 43 | 6 | 12·24
Italians | 12 | 10 | 2 | 16·66
Other nationalities | 27 | 27 | 0 | 0
Nationality unknown | 66 | 65 | 1 | 1·51
---------------------+----------+--------+---------+-------------
Total | 505 | 478 | 27 | 5·34
---------------------+----------+--------+---------+-------------

It is worthy of remark that half of all the positive cases were
mental patients, who were found to be affected with Trichinella
to well-nigh 12 per cent. Trichinosis was not, however, the cause
of death in any case. Very frequently the Trichinellæ were found
calcified and dead.

Conditions are similar in most countries of Europe, where, of course, the number of infected pigs is considerably smaller, but the disease depends less on this than on the way in which the pork is prepared.

Cases of trichinosis have been known to occur in nearly all the countries of Europe; further, in Egypt, Algeria, East Africa, Syria, India, Australia, and America. North Germany, more especially the Saxe-Thüringian states, is the classical land for epidemics of trichinosis; the mortality varies, but it may be very high.[306]

[306] For instance, extensive epidemics occurred in Hettstädt in 1863 (160 patients, 28 deaths); Hanover, 1864–1865 (more than 300 patients); Hadersleben, 1865 (337 patients, 101 deaths); Potsdam, 1866 (164 patients); Greifswald, 1866 (140 cases, 1 death); Magdeburg, 1866 (240 cases, 16 deaths); Halberstadt, 1867 (100 cases, 20 deaths); Stassfurt, 1869 (over 100 cases); Wernigerode, 1873 (100 cases, 1 death); Chemnitz (194 cases, 3 deaths); Linden, 1874 (400 cases, 140 deaths); Niederzwohren, near Cassel, 1877 (half the population); Diedenhofen, 1877 (99 cases, 10 deaths); Leipzig, 1877 (134 cases, 2 deaths); Ernsleben, 1883 (403 cases, 66 deaths); Strenz-Neuendorf, 1884 (86 cases, 12 deaths), etc. According to Johne, 109 epidemics, with 3,402 cases and 79 deaths, occurred in Saxony between 1860 and 1889. Stiles, in a work recently published, states that there were 8,491 cases of trichinosis with 513 deaths (6·04 per cent.) in Germany from 1860 to 1880; and 6,329 cases and 318 deaths (5·02 per cent.) between 1881–1898. Of these latter, 1881–1898, 3,822 (225 deaths) occurred in Prussia, 1,634 (76 deaths) in Saxony, and 873 (17 deaths) in the remaining states. There is, however, no doubt that many deaths from trichinosis were not recognized, as proved by experience at _post-mortems_.

_Prophylaxis._--The grave nature of the disease and the comparatively
high mortality relating to trichinosis led the authorities to adopt
certain preventive measures, which are the more necessary as national
customs cannot be altered in a short time. As the usual process of
pickling and smoking, even when long continued, does not certainly
ensure the death of the Trichinellæ contained in the meat, and also
because in roasting and boiling large pieces of pork a considerable
time is necessary to permit the temperature required to kill off the
parasites (62° to 70° C.) to penetrate to the middle of the joint,
it appeared to be most practical to have all pigs microscopically
examined for Trichinellæ before they, or parts of them, were placed
on the market, and all infected meat condemned, no matter whether the
Trichinellæ were present in large or small numbers, still undeveloped
or calcified. Since 1877 obligatory examination of pork has been
introduced in Prussia, though as yet it is not thoroughly carried
out; other states of North Germany as well as the larger towns of
South Germany soon followed; a complete army of trichina inspectors,
officially examined and periodically controlled by experts, and
whose number in Prussia amounted to 27,602 in 1896, this being even
increased to 28,224 in 1899, have the charge of examining pork on
certain lines laid down. These are at the present time uniformly
administered. The proceeding is usually that the trichina inspector
himself goes to the slaughterhouses, or special samplers take pieces
of the muscles that are known to be the favourite seats of the
parasite (pillars of the diaphragm, the costal part of the diaphragm,
muscles of the tongue and larynx, intercostal and abdominal muscles);
six small portions are separated from each piece, pressed between
slides or special compressors, and carefully gone through by
examining them with a low power of the microscope. The pigs free
from Trichinellæ are passed for commerce; trichinous pigs, on the
other hand, in Prussia, are only allowed to be used for industrial
purposes, _i.e._, the hide and bristles are used, the fat is allowed
to be melted down, or certain parts are used for the manufacture of
soap or glue. In Saxony, however, it is still permitted to place
trichinous flesh on the market, fully declaring its nature, and after
having been heated to its deepest strata at a temperature of 100° C.
in a suitable apparatus, and under the supervision of a veterinary
surgeon.

AS TO THE PROPORTION OF TRICHINOUS PIGS to healthy ones, the
following tables give the figures for Prussia:--