Chapter XXII: Appendix: “Rhizopods in Poliomyelitis acuta.” (16)

------+---------------+-----------------+------------
| Number of | Number of |
Year | pigs examined | trichinous pigs | Proportion
------+---------------+-----------------+------------
1878 | 2,524,105 | 1,222 | 1 : 2,065
1879 | 3,164,656 | 1,938 | 1 : 1,632
1881 | 3,118,780 | 1,695 | 1 : 1,839
1882 | 3,808,142 | 1,852 | 1 : 2,056
1883 | 4,248,767 | 2,199 | 1 : 1,932
1884 | 4,611,689 | 2,624 | 1 : 1,741
1885 | 4,421,208 | 2,387 | 1 : 1,852
1886 | 4,834,898 | 2,114 | 1 : 2,287
1887 | 5,486,416 | 2,776 | 1 : 1,988
1888 | 6,051,249 | 3,111 | 1 : 1,945
1889 | 5,500,678 | 3,026 | 1 : 1,818
1890 | 5,590,510 | 1,756 | 1 : 3,183
1891 | 6,550,182 | 2,187 | 1 : 2,996
1892 | 6,234,559 | 2,085 | 1 : 2,992
1896 | 8,759,490 | 1,877 | 1 : 4,666
1899 | 9,230,353 | 1,021 | 1 : 9,040
1902 | 9,093,210 | 725 | 1 : 12,397
------+---------------+-----------------+------------

The proportion, however, is not only subject to variation in separate
years, but differs according to the district; thus, in 1884, in the
state district of Minden there was one trichinous pig to 30,146
healthy animals, in Erfurt 1 to 14,563, in the district of Gnesen 1
to 101, in Schrimm 1 to 86, and in Schroda 1 to 68.

In Germany Trichinella is becoming LESS COMMON in pigs (Ostertag):--

(_a_) _Prussia._

Pigs found
Year to be trichinous
1878–1885 0·061–0·048 per cent.
1886–1892 0·033–0·043 "
1896 0·021 "
1899 0·014 "
1902 0·011 "

(_b_) Saxony.

Number of pigs
Year found to be trichinous
1891 0·014 per cent.
1892 0·011 "
1893 0·008 "
1894 0·007 "
1895 0·012 "
1896 0·0102 "
1899 0·004 "
1902 0·0056 "

(_c_) City of Berlin.

Number of pigs
Year found to be trichinous
1883–1893 0·035–0·064 per cent.
1893–1897 0·022–0·015 "
1902 0·006 "

There is no doubt that the excellent preventive measure of official inspection for Trichinella has led to the avoidance of grave disasters; its introduction has not yet caused an entire cessation of trichinosis in man, because inspection of pork is not obligatory everywhere, so that human beings may become infected by unexamined trichinous pigs from their own country or from abroad, and also because an infection may occasionally escape notice. For these reasons the meat imported into Berlin from abroad as free from Trichinæ is examined again and not always in vain; finally, also, gross negligence may at times occur, or fatal errors may be made.

In addition _private prophylaxis_ must not be neglected, and its chief aim should be directed to the suitable preparation of pork.

Family. *Dioctophymidæ.*

Genus. *Dioctophyme*, Collet-Megret, 1802.

Syn.: _Eustrongylus_, Dies., 1851.

Large worms. Anterior extremity unarmed; the mouth is surrounded by
six papillæ. One ovary. The vulva is in the anterior region of the
body.

*Dioctophyme gigas*, Rudolphi, 1802.

Syn.: _Dioctophyme renale_, Goeze, 1782; _Ascaris canis_ et _martis_,
Schrank, 1788; _Ascaris visceralis_ et _renalis_, Gmelin, 1789;
_Strongylus gigas_, Rud., 1802; _Eustrongylus gigas_, Dies., 1851;
_Strongylus renalis_, Moq. Tand., 1860; _Eustrongylus visceralis_,
Raill., 1885.

Colour blood-red; the anterior extremity somewhat slender; there is a series of about 150 papillæ along the lateral lines; the sub-median lines are strongly developed, and from them spring the radial muscles for the intestine.

The males attain a length of 40 cm. and a diameter of 4 to 6 mm.; the posterior extremity is transversely truncated; the anal orifice is within the base of the collar-like bursa, the thickened edges of which are beset with papillæ; the spicule measures 5 to 6 mm. in length.

The females attain a length of 100 cm. and a breadth of 12 mm. The anus is crescent-shaped and terminal. The vulva is 50 to 70 mm. distant from the anterior extremity. The eggs are oval and have a thick shell presenting numerous depressions; the shell itself is brownish, but it is colourless at the somewhat thickened poles; it measures 60 µ in length by 40 µ in breadth. The larva measures 240 µ by 14 µ.

_Dioctophyme gigas_ lives in the pelvis of the kidney, more rarely in the abdominal cavity of the seal, otter, dog, wolf, fox, horse, marten and polecat, exceptionally also in human beings. It also occurs in tumours of the mamma and perinæum. Most of the cases in which this parasite has been reported as occurring in man may be traced back to unrecognized _Ascaris lumbricoides_ or to clots of fibrin; seven certain cases, eight more or less doubtful, however, remain.

The source of infection is unknown, but according to Balbiani the eggs develop an embryo in water or moist soil, and this embryo may remain alive several years without hatching; the infection of dogs with embryo-containing eggs did not succeed; an intermediate stage in fishes is conjectured, but still the infection of cattle and horses is unintelligible.

Family. *Strongylidæ.*

Sub-family. *Metastrongylinæ*, Leiper, 1908.

Buccal capsule absent or slightly developed, vagina elongate, uteri convergent[307] and have a simple musculature. Parasitic in the respiratory or circulatory system. Genera: Metastrongylus, Synthetocaulus.

[307] Convergent: _i.e._, the uteri are parallel, converging from the anterior part of body to the vagina, which is near the anus, this position being associated with convergence of the uteri. Divergent: Uteri run anterior and posterior, diverging from the vagina, which in this case is near middle of body.

Genus. *Metastrongylus*, Molin, 1861.

Mouth with six lips, of which the two lateral are the largest. Postero- and postero-external rays[308] of bursa thin, the rest thick. Only the median ray double. Spicules very long and slender, striated. Vulva immediately in front of anus. Eggs contain an embryo when laid.

[308] For nomenclature of rays _vide_ p. 449.

*Metastrongylus apri*, Gmelin, 1789.

Syn.: _Gordius pulmonalis apri_, Ebel, 1777; _Ascaris apri_, Gmelin,
1789; _Strongylus suis_, Rud., 1809; _Strongylus paradoxus_,
Mehlis, 1831; _Strongylus elongatus_, Duj., 1845; _Strongylus
longevaginatus_, Dies., 1851.

The male measures 12 to 25 mm. in length; the bursa is bilobed; there are five rays in each lobe; the spicules are thin and up to 4 mm. in length. The females measure 20 to 50 mm. in length, the anus is close in front of the posterior extremity, which has a recurved, hook-like process; the vulva is close in front of the anus. The eggs are elliptical, 57 µ to 100 µ in length, 39 µ to 72 µ in breadth; when the eggs are deposited the embryo is already formed, 220 µ to 350 µ by 10 µ to 12 µ.

_Metastrongylus apri_ frequently lives in the bronchial tubes--usually the smaller ones--of the pig[309] and wild boar; it is also found occasionally in sheep and in man; in young pigs it is apt to set up a bronchitis, which frequently causes death.

[309] The reports of the city inspection of meat in Berlin state that _Strongylidæ_ in the lungs of pigs are by no means rare; therefore the lungs of 1,941 pigs were condemned between 1885–1886, of 1,641 between 1886–1887, of 3,237 between 1887–1888, of 4,855 between 1888–1889, of 7,197 between 1889–1890, and of 5,574 pigs between 1890–1891, etc. Ostertag found _Strongylus apri_ in 60 per cent. of the pigs examined in the Berlin abattoir; Meyer, in Leipzig, found the parasite in 15 per cent. of the native pigs and in 52 per cent. of the Hungarian pigs.

The first communication as to the occurrence of this species in man was that of Diesing, who, in 1845, in Klausenburg, had the opportunity of examining _Strongylidæ_ found by Jortsits in the lung of a little boy, aged 6, in Transylvania; probably also the Nematodes found in the trachea and larynx of man, and described by Rainey and Bristowe as specimens of _Filaria trachealis_, belong to this group; according to Chatin, _Metastrongylus apri_ may also occur in the intestine of man; this occurrence, however, may in all probability have been due to an accidental introduction of adult worms into the intestine, and should not be attributed to an infection by the larval stage.

No experiments to induce infection have been made; it is probable, however, that infection is direct and without the aid of an intermediate host.

Sub-family. *Trichostrongylinæ*, Leiper, 1908.

Strongylidæ with buccal capsule absent or slightly developed, vagina short, uteri divergent (_i.e._, anterior and posterior), ovejectors differentiated. Parasitic in the alimentary canal. Contains the genera Trichostrongylus, Hæmonchus, Ostertagia, Nematodirus, Cooperia, Dictyocaulus.[310]

[310] _Dictyocaulus_ is parasitic in the bronchi.

Genus. *Trichostrongylus*, Looss, 1905.

Very small _Strongylidæ_. Mouth with three small lips and nodular or punctiform papillæ. Cervical papillæ absent. Bursa entirely closed, with large lateral lobes, and median lobe not distinctly defined. Anterior[311] rays double, the branches widely divergent, one thin, the other thick, and close to the antero-median. The postero-median ray is thin and close to the postero-external. Posterior ray bifurcate, each branch bifid at the tip (fig. 311). Spicules short, spoon or spatula-like, with on the broad anterior end a lateral knob or disc and in front of the point an angular projection. Gubernaculum of a peculiar canoe or shoe shape in profile. Vulva in the hinder half of the body. Tail with two minute papillæ just in front of tip. Eggs thin shelled; when laid they show eight to thirty-two segments. Parasitic in duodenum, seldom in the stomach of herbivora.

[311] When the anterior ray is double, the branches of it are called antero-anterior and latero-anterior.

*Trichostrongylus instabilis*,[312] Railliet, 1893.

[312] Identical with _T. colubriformis_ of the sheep according to Leiper. If so, this latter name has priority.

Syn.: _Strongylus instabilis_, Railliet, 1893; _Strongylus subtilis_,
Looss, 1895.

Male 4 to 5·5 mm. long, 0·08 mm. thick in front of bursa. Spicule 0·135 to 0·145 mm. long, accessory piece (gubernaculum) 0·07 mm. thick. Antero-external ray usually thickest of all, occasionally only as thick as the antero-median; postero-median far more slender than the antero-external and antero-median and nearer to the postero-external than to the antero-median. Female 5 to 6 mm. long, vulva 1·05 to 1·2 mm. distant from the tip of the tail, placed _longitudinally_, 50 µ to 55 µ long, always shorter than the unpaired portion of the canal formed by the union of the two ovejectors; anus 0·055 to 0·07 mm. distant from tip of the tail; ova 73 µ to 80 µ by 40 µ to 43 µ.

This species lives in the duodenum, exceptionally also in the stomach of _Ovis aries_, _O. laticauda_, _Antilope dorcas_, _Camelus dromedarius_ (Egypt), _Cynocephalus hamadryas_ (North Africa), sheep and goats (France), and has been found by Looss in bodies of fellaheen at Alexandria and in the stomach of a Japanese female by Ijima.

*Trichostrongylus probolurus*, Railliet, 1896.

Syn.: _Strongylus probolurus_, Railliet, 1896.

Male 4·5 to 5·5 mm. long, in front of bursa 0·08 mm. thick; spicule 0·126 to 0·134 mm. long, gubernaculum 0·075 to 0·08 mm. long. Bursa: latero-anterior rib thickest; antero-external thicker than antero-median, postero-median and postero-external very short and close together. Female 4·5 to 6 mm. long, vulval opening 1·08 to 1·25 mm. from tip of tail, placed _longitudinally_, and slightly curved, 76 µ long, always longer than the unpaired portion of the ovejector; anus 0·040 to 0·05 mm. distant from tip of tail. Posterior end thick, point of tail short. Ova 76 µ to 80 µ by 43 µ to 46 µ.

_Habitat._--In the duodenum of _Ovis aries_, _O. laticauda_, _Antilope dorcas_, _Camelus dromedarius_ (Egypt) and occasionally also in man (Egypt).

*Trichostrongylus vitrinus*, Looss, 1905.

Male 4 to 5·5 mm. long, in front of bursa 0·085 mm. thick. Bursa larger than in the other two species, antero-external rib thickest, antero-anterior and postero-median equally thick, straight. Spicule 0·16 to 0·17 mm. long, gubernaculum 0·085 to 0·095 mm. long. Female 5 to 6·5 mm. long, vulval opening 1·15 to 1·25 mm. distant from tip of tail, crescent shaped, _oblique_ to body axis, and around it irregular thickenings. Ova 84 µ to 90 µ by 46 µ to 50 µ.

In duodenum of _Ovis aries_, _O. laticauda_, occasionally in _Camelus dromedarius_ and in man (Egypt).

Genus. *Hæmonchus*, Cobb., 1898.

Small mouth cavity contains a “tooth” or “lancet” arising from the dorsal side. Cuticle of head and neck not inflated. Cervical papillæ well marked. Bursa bilateral, with large lateral lobes and a small dorsal lobe _not median_, but lateral, attached to the base of one of the lateral lobes (fig. 316). Posterior ray bifurcate, each branch bifid apically. Each lateral lobe six rays. Anterior rays separated distally, curving forward. Antero-median and postero-median rays distally curve away from the antero-external. Postero-external ray long and slender. Spicules less than 1 mm. Gubernaculum present. Vulva in posterior part of body covered by a prominent tongue-like flap. Eggs ellipsoidal.

*Hæmonchus contortus*, Rudolphi, 1803; Cobb., 1898.

Dorsal “tooth” or “lancet” 10 µ to 15 µ long. Cervical papillæ 0·3 mm. from head.

Male 20 mm. long by 400 µ thick (maximum). Asymmetrical lobe of bursa 150 µ by 125 µ attached to left lateral lobe. Posterior ray bifurcate; each branch bifid. Stem of ray less than twice as long as its branches. Spicules 300 µ to 500 µ with knobbed tips, and the left spicule with a barb 20 µ from the tip, right spicule with a barb 40 µ from tip. Gubernaculum 200 µ by 25 µ to 35 µ, fusiform with thickened edges.

Female 18 to 30 mm. by 500 µ (maximum). Vulva 3 to 4·5 mm. from tip. Linguiform flap 0·5 mm. (a second one exists, according to Brumpt). Anus 400 µ to 630 µ from tip. Tail acutely pointed. Eggs 75 µ to 95 µ by 40 µ to 50 µ.

_Habitat._--Fourth stomach of cattle, sheep, antelope.

_Distribution._--Europe, America, Africa, Asia, Australia, New Zealand. Once in man in South America by de Magalhães.

_Pathology._--Produces anæmia, emaciation, dropsy in sheep; and in the human case the symptoms were mistaken for those of ancylostomiasis.

_Life-history._--Rhabditic embryos easily hatch in water, then moult several times, becoming eventually “filariform” larvæ enclosed in the moulted skin. These crawl up blades of grass and are swallowed by sheep, etc.

Genus. *Nematodirus*, Ransom, 1907, emend. Railliet, 1912.

Head over 50 µ in diameter. Cuticle may be slightly inflated and often transversely striated. Cuticle with eighteen distinct longitudinal ridges. Cervical papillæ absent (?). Posterior lobe of bursa reduced to short lobules each with a dorsal ray. Antero-anterior + latero-anterior (= anterior double) rays close together, parallel; antero-external ray diverges widely from antero- and postero-median, which are close together and parallel. Postero-external ray slender. Spicules more than 0·5 mm. long, at most one-twelfth of body, united by a membrane throughout their length or only distally. Gubernaculum absent. Vulva behind middle of body. Eggs ellipsoidal, shell rather thick.

_Habitat._--Duodenum of ruminants.

Sub-genus. *Mecistocirrus*, Railliet, 1912.

Head slightly inflated, with transverse striations. Skin with eighteen longitudinal ridges, but little apparent; cervical papillæ distinct. Bursa bilobed; median ray double (= postero-median + antero-median); very large antero-external at the edge, close to the anterior. Spicules very long, slender, one-sixth length of body (3·5 mm.); tail pointed. Vulva immediately in front of anus.

_Habitat._--Stomach of ruminants.

*Mecistocirrus fordi*, Daniels, 1908.

Syn.: _Strongylus fordi_, Daniels, 1908; _Strongylus gibsoni_,
Stephens, 1909; _Nematodirus fordi_, Leiper, 1911.

Male 21 mm. long by 0·4 mm. thick. Cervical papillæ 0·45 mm. behind the head. Spicules about 7 mm. long, _i.e._, one-third of the body length. At the level of the postero-external rays of the bursa, the bursa has a projecting lobule.

Female 25 mm. long. Anus 0·2 mm., vulva 0·5 mm. from the tip of tail. Eggs 100 µ by 53 µ.

Sub-family. *Ancylostominæ*, Railliet, 1909.

_Strongylidæ_ with buccal capsule, well developed. Uteri divergent. Parasitic in the alimentary canal, exceptionally in the respiratory system.

Group. *Œsophagostomeæ*, Railliet and Henry, 1909.

Bursa with anterior and median ray cleft (not double), postero- and postero-external arising from a common trunk, posterior bifurcated, each limb bidigitate.

Contains at present four genera: (1) Ternidens, (2) Chabertia, (3) Œsophagostomum, (4) Agriostomum.

Genus. *Ternidens*, Railliet, 1909.

Buccal capsule sub-globular, opening obliquely in the dorsal surface, and having at the bottom three complex teeth resembling those of Triodontophorus.[313] Two crowns of leaflets; peristomic collar moderate, edge of bursa slightly toothed.

[313] Triodontophorus belongs to the group _Cylicostomeæ_, which has the following bursal formula: (1) anterior cleft, (2) median double, (3) postero-external and posterior arising _separately_, (4) posterior double, each branch giving off two lateral branches.

_Type._--_T. deminutus_, Railliet and Henry.

*Ternidens deminutus*, Raill. and Henry, 1905.

Syn.: _Triodontophorus deminutus_, Raill. and Henry, 1905.

Body relatively thick. Cervical papillæ 0·5 mm. behind the head. Buccal capsule 40 µ deep. Teeth 40 µ long.

Male 9·5 mm. long by 560 µ thick. Œsophagus 660 µ long. Bursa broader than long, the lateral lobes united by a small posterior lobe with slightly sinuous margin; edge of bursa finely toothed. Spicules about 900 µ long.

Female 12 to 16 mm. long by 650 µ to 730 µ thick. Œsophagus 860 µ long. Vulva forms a distinct projection 480 µ from tip of tail. Anus 240 µ to 270 µ from tip. Eggs 60 µ to 80 µ by 40 µ.

_Habitat._--Large intestine of a negro (Comoro Islands) and in the natives of Nyasaland and Portuguese East Africa. Also in large intestine of _Macacus sinensis_ and _Macacus cynomolgus_.

Genus. *Œsophagostomum*, Molin, 1861.

No teeth. Cuticle around the mouth dilated to form a narrow cuticular “peristomic collar.” Separated by a constriction from this is a much more extensive inflation, the “cephalic vesicle,” bounded abruptly behind on the ventral side by a transverse groove, the “ventral cleft,” which is always present even in absence of the vesicle. Buccal cavity of slight depth with a short dorsal tunnel. Internal margin of the mouth armed with chitinous leaflets (“external crown”); internal border of the buccal capsule armed with short tongue-like leaflets (internal crown). Lateral membranous wings may extend backwards from the ventral cleft. Cervical papillæ present. Bursa with two lateral lobes united by a smaller median lobe. Spicules over 5 mm. long, slender; gubernaculum inconspicuous. Vulva in front of anus. Adults usually in large intestine of ruminants, suidæ, tapirs, edentates and apes. Larvæ sometimes in nodules in intestinal wall.

*Œsophagostomum brumpti*, Railliet and Henry, 1905.

Female immature, 8·5 to 10·2 mm. long, 0·295 to 0·325 mm. thick. Cuticle transversely striated. The cephalic vesicle immediately behind the vestibulum oris, embracing the anterior two-fifths of the œsophagus, extending ventrally, however, towards its posterior end. Vestibulum oris formed by a cuticular band provided with a crown of twelve apical leaflets directed forward and inwards; six cephalic papillæ (two lateral, four submedian); buccal capsule in front of cervical swelling not delineated circularly behind, but provided with three wide incisions (one dorsal, two sub-ventral). Œsophagus, 0·470 to 0·500 mm. long, two cervical papillæ at five-eighths of its length. Vulva 0·350 to 0·475 mm., anus 0·170 to 0·200 mm., before tip of tail.

_Habitat._--Found by Brumpt in tumours of the cæcum and colon of a native of the River Omo (Lake Rudolph), East Africa. Immature forms only were present. Adults have been found in similar tumours in monkeys.

_Pathology._--They occur in hæmorrhagic cysts in the submucosa or muscularis mucosæ of the gut wall. The cysts project internally and externally, and contain immature adults, which eventually escape into the lumen of the gut.

*Œsophagostomum stephanostomum* var. *thomasi*, Raill. and Henry, 1909.

Body thick, pointed only at the ends. Buccal capsule much reduced. External crown of thirty-eight leaflets (the “crown” nearest the centre of fig. 319, 5). Male 17 to 22 mm. long by 750 µ thick. Spicule 1·380 to 1·475 mm., slightly curved at the tip. Female, immature, 16 to 20 mm. long by 900 µ thick, tail ending in a little conical appendage. Anus 230 µ, vulva 500 µ to 525 µ from tip. Ovejectors close together. Uteri very short in form of oblong pouch.

_Œs. stephanostomum_, Stossich, 1904, in the large intestine of gorilla. _Œs. stephanostomum_ var. _dentigera_, Raill. and Henry, 1909, in the chimpanzee.

_Habitat._--In large and small intestine of man, Brazil.

_Pathology._--Nodules occur in the gut wall; 187 were found by Thomas in his, the sole case. The tumours contain each a single worm.

*Œsophagostomum apiostomum*, Willach, 1891.

According to Leiper, _Œs. brumpti_ is identical with, and hence a synonym of, this species. Parasitic in large intestines of monkeys, producing dysentery, and in man (Northern Nigeria).

According to Walker this species is common in Philippine monkeys. Ova are scanty in the fæces. They measure 73 µ to 84 µ by 44 µ to 57 µ and are in the morula stage. They are easily cultivated. The rhabditiform larva is 340 µ by 16 µ and has a long filiform tail. It moults twice, and at the second moult becomes a filariform larva retaining the skin of this moult, this stage being that of the mature larva. It now measures 9 mm. long by 30 µ thick. Walker suggests that the mode of infection is similar to that of ancylostomes.

Group. *Ancylostomeæ*, Railliet and Henry, 1909.

Bursa with anterior ray cleft, median double,[314] postero- and postero-external arising from a common trunk, posterior bifurcate, each limb being tridigitate. Vulva in posterior third of body. Uteri divergent.

[314] _I.e._, with a distinct space between the limbs.

Contains the following genera: (1) Strongylus,[315] (2) Ancylostoma, (3) Uncinaria, (4) Characostomum, etc.

[315] Strongylus (Syn.: Sclerostomum) differs slightly in its posterior ray from the other genera of the group. Each bifurcation is trifurcate rather than tridigitate.

Genus. *Ancylostoma*, Dubini, 1843, emend. Looss, 1905.

Ventral margin of mouth capsule armed with teeth, the “roots” of which are continued backwards and appear on the _external_ surface of capsule as rib-like thickenings. Terminal third of dorsal ray cleft. Genital tubes very long, with short, closely packed diagonal convolutions.

*Ancylostoma duodenale*, Dubini, 1843.

Male 9 mm. long by 0·45 mm. thick, female 12 mm. long by 0·6 mm. thick. Pale flesh colour, or an intense red in posterior third. Anteriorly may be more or less black due to (blood) pigment in the cells of the chyle intestine (= stomach + small intestine). The worm is about the same thickness all through and is plump and rigid. Cuticle striated. The body has a marked torsion, so that if the ventral side of the head is upwards the anus appears to open laterally and _vice versâ_. The dorsal curve of the head end is only slight and the œsophagus is roughly cylindrical.

_Buccal Capsule._--The buccal capsule is bent dorsally, 0·21 mm. long, 0·19 mm. broad. If a worm is rolled under the cover-glass so that the dorsal side is upwards, we observe the following features (fig. 325): In the dorsal edge of the chitinous capsule there is a gap as if a *U*-piece had been punched out. This is the “dorsal gap or incision.” The so-called “dorsal teeth” are simply the rounded edges of the tips of this gap. They project _beyond_ the skin which covers the capsule externally. Below this gap is seen a curved line which, if followed along the sides of the capsule on each side, merges into the base of the most posterior ventral tooth. This line is the optical expression of a very shallow groove on the _inside_ of the capsule. The skin on the outside of the capsule, which is reflected over the edge of and into the capsule, dips into this groove, which gives it a firm attachment. Below the middle (dorsally) of this curved line there is a thickening in the capsule wall, which is perforated by the opening of the dorsal œsophageal gland. This is the “dorsal ridge”; in optical section it has a conical appearance with a lumen (of the duct).

On the ventral wall one sees the two pairs of strong teeth, their points being directed somewhat backwards. They are covered by cuticle above and below, but their points are free, piercing the cuticle. The “roots” of these teeth followed backwards appear as two thickenings or ribs on the _outside_ of the capsule wall, so that the outside wall is not smooth--a characteristic of the genus Ancylostoma. In the space between these ribs lies the ventral nerve papilla, and lying against the outside of the outer root the lateral nerve papilla. The nerve papillæ are thus, as it were, concealed by these roots, and not conspicuous as they are in Necator. Following the ventral curve of the capsule on the inside, posteriorly we next find two triangular ventral lancets.[316] These stand straight up into the capsule on either side of the longitudinal axis, converging at their summits. So that to sum up, the cutting apparatus is entirely ventral, consisting of two pairs of cutting teeth and a pair of lancets.

[316] The ventral lancet (of one side) of Necator is seen in fig. 335.

_Cervical Papillæ._--Two, one on each side behind the head at the level of the excretory pore. They consist of “pulp,” _i.e._, extensions of the substance of the lateral bands covered by cuticle and supplied with a nerve (fig. 326).

_Œsophageal Glands_ (3).--The chitin of the triradiate œsophagus is continuous with that of the buccal capsule. In its muscular walls are three glands--one dorsal, two sub-ventral. The dorsal gland opens into the buccal cavity through the dorsal ridge; the two others into the lumen of the œsophagus at the nerve ring. They branch freely amidst the muscles. They are probably digestive in function.

_Cephalic Glands_ (2).--Lie in the lateral lines or bands on either side. They begin about the middle line of the body, and their ducts open at the base of the outer ventral tooth on the surface of the skin on each side. Each is 0·15 mm. thick in the middle, and has a single nucleus about as big as an ancylostome egg (_N_, fig. 323). They probably function as poison glands.

_Excretory System and Cervical Glands_ (2).--The excretory pore lies in the mid line ventrally behind the œsophageal nerve ring (figs. 324 and 326). It opens into the excretory vesicle, a cavity in a large cell with lateral appendages which fuse with the lateral lines, this cell thus forming the “bridge” of the excretory system. Adhering to this (bridge) cell are the spindle-shaped cervical glands (_Glc_, fig. 324), and branches from the excretory vesicle enter the glands, which are excretory in function; the vesicle also receives branches from the lateral excretory canals (fig. 326) running in the lateral lines or bands. The cervical glands are swollen anteriorly, forming the so-called ampullæ just in front of the bridge. They extend backwards a little beyond the anterior loop of the testis.

_Lateral Lines._--(1) Are broad elevations of the subcuticle, in which, here and there, a nucleus occurs. (2) Near the bursa in the male they increase in volume, and finally divide into branches which form the “pulp” of the different rays. (3) In addition to the lateral lines or bands, there is also a dorsal and ventral band. (4) The ventral band is well developed caudally, forming a large pad dorsal to the cloaca, “pulvillus post-analis.”

The bursal rays are outgrowths of the lateral lines. Beside this “pulp” they contain a nerve, and at their bases complex muscles.

_The Bursa_ is closed on all sides with a short median (ventral) lobe, which may be tucked inwards. It is an outgrowth of the inner layer of the skin pushing the outer layer before it, so that it consists of three layers, not four, as it would be if it were a fold. The bursa is twice as broad as long. It is supported by a variety of rays, the arrangement of which is best followed from the figure (fig. 327). The different terminology for these rays as used by various authors should be noted: Ventral = anterior; externo-lateral = antero-external; medio-lateral + postero-lateral or antero-median + postero-median = median (doubled); externo-dorsal = postero-external; dorsal = posterior. All the rays end in tactile papillæ, seven, on each side; the postero-external and antero-external on the _outer_ surface of the bursa, the five others on the _inner_ surface.[317] Of the six terminal digitations of the _dorsal_ ray, only the external two contain tactile papillæ.

[317] This also occurs in other _Strongylidæ_, _e.g._, in the genus Strongylus (Syn.: Sclerostomum).

In the male there are prebursal papillæ and minute caudal papillæ in the female.

In the female the inner layer of the cuticle projects at the posterior end as a sharp spike, 20 µ long, which may sometimes be broken off.

_Ovaries._--The anterior tube runs from the cephalic to the posterior end and back again. The posterior tube begins anteriorly, runs to the posterior end of the body, and then back to the cephalic end, forming a vulval loop before ending. The ovaries on the whole run in oblique coils. The uterus is the thicker portion of the tube, 5 mm. long. A short tube connecting the ovary and uterus is the oviduct. The two uteri unite to form a single duct, the vagina, opening 1 mm. _behind_ the middle line. The portion of the uterus next to the oviduct functions as a seminal receptacle, whereas the part next the vagina functions as an ovejector.

_Testis._--The blind end begins a little behind the beginning of the _cement gland_. The transverse coils occupy the middle third of the body. About the middle of the body it passes into the spindle-shaped seminal vesicle, which, with the spicular canal and rectum, opens into the cloaca. An anterior longitudinal coil pushing in between the cervical glands is characteristic of Ancylostoma. The cement gland surrounds the ejaculatory duct for practically its whole course, and it occupies nearly the posterior half of the body and secretes a brown or black cement. The spermatozoa are curved rods about 2 µ long.

_Spicules_ are 2 mm. long, ending in a fine point. They are moved by exsertor and retractor muscles. At first they lie free in the body cavity; next in a groove in the dorsal wall of the cloaca; then in an isolated canal, and finally in two canals. Anteriorly each has two longitudinal crests on its inner surface. These meet the corresponding crests of the other spicule, and so form a canal along which the sperm passes into the female. The gubernaculum is a thickening of the dorsal wall of the cloaca. It is not a free piece, but is moved by various muscles.

_Genital Cone_ is a prominence on the floor of the bursa on the ventral side of the body, on which the genito-anal orifice opens. The cone is only slightly marked in _Ancylostoma duodenale_, but is much more prominent in _Necator americanus_.

_Distribution._--Africa, Egypt, Europe, Japan, China (mainly), but in association with _Necator americanus_ in Southern States of America, British India, Assam, Burma, Hongkong, Liberia, Jamaica, Martinique, Costa Rica, Colombia, Antigua, Guadeloupe.

_Habitat._--The worms live in the jejunum, less frequently in the duodenum, of man only.

_Food._--The worms feed on the mucous membrane of the gut, attaching themselves to the base of the villi, sucking these in; and when these are destroyed they attack further the submucosa. As a rule the worms have no blood in the gut, but in their attack on the submucosa a blood-vessel may be eroded, and so the gut of the worm filled with blood.

_Development._--The eggs are oval with broadly rounded poles, 56 µ to 61 µ by 34 µ to 38 µ. In _fresh_ fæces they contain four granular nucleated segmentation masses of the ovum (fig. 329) separated by a clear space from the shell.

_Egg of Ancylostome_ appears to have a single contour. Under high powers this appears double, but they are the outer and inner surface of the true (chitinous) egg-shell. Internal to this is the extremely delicate yolk-envelope, a kind of skin secreted by the egg cell around itself for protection. The function of this is probably to absorb water to swell and burst the outer chitinous shell. The embryos when hatched are termed larvæ.

_Embryos_ which are ready to hatch have their bodies almost free from granules; others, though apparently mature, that have granules will not hatch.[318]

[318] TABLE OF DIFFERENCES BETWEEN LARVÆ OF _A. duodenale_ AND _S. stercoralis_.

--------------+----------------------+------------------------------
| _A. duodenale_ | _S. stercoralis_
--------------+----------------------+------------------------------
(1) Vestibulum| | }
oris |1·8 µ broad |3 µ }Rhabditiform.
(2) Genital | | }
rudiment|3 µ to 5 µ long |25 µ to 33 µ }
| |
(3) Thickness |Thicker | -- }
(4) Œsophagus |One-fourth body length|Half body length}
(5) Tail |Pointed |Two fine points }Filariform.
(6) Motion |Less active than | -- }
(7) Gut |Soon fills with dark | }
| granules | -- }
--------------+----------------------+------------------------------

_Larva._--_Stage I_: Average length, 25 mm. Maximum thickness in œsophageal region, 17 µ. Head end fairly blunt, from behind the anus (the tail) tapering in an uniform manner. Buccal cavity is characteristic, 10 µ to 12 µ by 1 µ to 8 µ, longer and narrower than the corresponding larvæ of _Strongyloides stercoralis_. Œsophagus “rhabditic” in character, _i.e._, it has three sections, but they are not so clearly marked off as in larvæ of the genus Rhabditis. The posterior bulb has a *Y*-shaped valve, the function of which, according to Looss, is to prevent regurgitation of food. The granules of the gut serve as a reserve of food, and are used up if the larvæ are starved. The _genital rudiment_ consists of two cells half-way between the end of the œsophagus and the anus in the mid-ventral line. The larva lives on fæcal matter and grows to about 0·4 mm., then moult[319] I takes place in two days or more, the skin being ruptured by the activity of the larva.

[319] Moults take place by the formation of a new skin below the old one, the two being in close apposition at first.

_Stage II_: The larva is now in this stage, which does not differ much from the previous one. It grows to 0·5 mm. The mouth opening closes. The œsophagus elongates, becoming cylindrical or “filariform”; a new skin is formed underneath the old one, and in about a week moult II takes place.

_Stage III_: The _mature larva_ remains enclosed in the old skin. Its movements are now much more active and of a boring character. Length is now 0·6 mm. This mature stage has been erroneously called the encysted larva, because there is no cyst _secreted_ from its surface by the larva, but it is simply the old skin, which is not cast off, but is retained for purposes of protection, as the larva is free living, but casts it as soon as it assumes parasitic life again. From the egg to this mature stage is thus six to ten days.

_Bionomics of Development._--_Air_: Eggs can develop when shut off from the air for a “comparatively long” time.

_Temperature_: Hatching takes from eight hours upwards. Eggs develop best at 25° to 30° C., but will not develop below 8° to 10° C. The larvæ, however, will stand freezing.

_Moisture_: Eggs and larvæ do not live long under water, because they suffocate or starve, but _mature_ larvæ will live for months (six to twelve) in water; they require no food--in fact, can take none in--but live on their reserve granules, and in course of time become as clear as glass.

_Thigmotropism_: The mature larvæ, after casting their skin, will penetrate pith, climb up stems, stalks, etc., and creep into any pore.

It is important to recognize that this third stage of the _mature larva_ is the only infective one.

_Mode of Entry into the Body._--Infection is effected through the mouth (Leichtenstern and others), and also through the skin, as was first discovered by Looss and afterwards confirmed from the most diverse quarters, partly in the case of _Ancylostoma duodenale_, partly in that of _A. caninum_ in dog, man, and monkey. The larvæ that gain access to the intestine partly through contaminated food, or through unwashed hands, or under some circumstances through water, first throw off their “sheath”--that is, they complete moult II. Moult III takes place four to five days after they have reached the gut, and they now have a mouth capsule supplied with four small teeth arranged crosswise, enabling them to fasten on to the intestinal epithelium, upon which they feed. On this food the worms grow in four to six days to 3 to 5 mm. in length, and now moult IV. takes place, thus attaining their definite shape and distinctive character. About eight days later the sexual organs commence to function; at this time the first copulation should be taking place--it will later be frequently repeated--and a few days later the first ova are laid, first in less and later in larger numbers, so that they appear in the fæces about four to five weeks after the infection.[320]

[320] From the number of eggs present in a given quantity of fæces, the number of female Ancylostomes present in the gut can be reckoned by a formula of Leichtenstern’s (x = _a_/47, in which _a_ signifies the number of eggs counted in a single gramme of fæces).

_Infection by the Skin._--Mature larvæ, which are placed on the skin of man or suitable animals, cast their “sheath” and bore their way through delicate fissures either horizontal in the superficial scales of the epidermis, or through vertical fissures into hair follicles where these exist, and then they invade the cutis. Now according as they migrate further into the lymphatic vessels or the small vesicles, the final path to the gut differs to some extent. The blood path leads to the right heart, and from there into the lungs; here the larvæ leave the blood stream and enter the air passages, over the mucosa of which they travel further headwards, through the bronchi into the trachea and larynx, and from hence through the œsophagus to the stomach; in some cases also they are swallowed. The lymphatic path leads finally also into the blood stream, but the lymphatic glands must first be passed, and in these many larvæ are retained and perish. In the cutaneous infection seven to ten weeks elapse till the time of appearance of the first ova in the fæces.

The penetration of the skin by the larvæ also in man causes reddening
and burning at the affected points, and this is followed in a
few days by transitory swelling in the subcutaneous connective
tissue. Skin affections can also be set up by such Ancylostoma
(and Strongyloides) larvæ as do not gain access to the blood or
lymphatic vessels or gut; such larvæ apparently wander further in the
connective tissue, and, as Looss has in his own person observed, gain
access to the cutis at different points, thus causing progressive
swellings (accompanied by intense itching), which cease when the
worm again penetrates into the deep tissues. Skin affections such
as “ground-itch” or “pani-ghao” occurring in the tropics and only
attacking the feet, or other affections (_e.g._, sump bunches) are
now well recognized as being due to the invasion of Ancylostoma larvæ.

Other names for these skin affections are water-sore, sore feet of
coolies, maza-morra, bunches, botches, quaddeln, krätze, ampoules,
gourmes, taons, pitirr. Whether oral or dermal infection is the more
important one further observation must decide.

The duration of life of _Ancylostoma duodenale_, which is a specific parasite of man and has not been observed in other mammals, amounts to about five years, as strayed larvæ according to Looss wander for this extent of time in the body.

_Cultivation of Larvæ._--(1) Mix the fæces (free from drugs such as salines or thymol) with animal charcoal, adding water if necessary till a consistence of porridge is obtained. If the stools are very fluid, allow to sediment first and pour off the fluid. The best charcoal is that made from bones, and should not have an acid reaction. Charcoal is necessary in order to prevent fermentation, which kills the larvæ. Spread in layers 2 to 3 mm. thick in Petri dishes. Incubate at room temperature. To extract the larvæ from the culture allow the surface thoroughly to dry, then pour on water; the larvæ wander out and are poured off and subsequently further purified by sedimentation or filtering through blotting paper, the larvæ passing through.

(2) A funnel is plugged with cotton wool, then filled with washed sand to within a centimetre or two of the rim. Stand this in a jar of water so that the level of the water is slightly below that of the sand. On the surface of the wet sand now place layers of blotting paper, and spread the fæces, diluted if necessary, on this in layers of a few millimetres thick (_vide_ p. 474).

_Detection of Eggs._--_Vide_ p. 473.

_Dermal Infection of Dogs._--Infection with larvæ of _A. caninum_. In two hours most of the larvæ are free in the cutis and in four hours in the subcutaneous tissue. By scraping a few days later the mucosa of the trachea large numbers of larvæ are found there.

*Ancylostoma ceylanicum*, Looss, 1911.

At the anterior edge of mouth capsule one large tooth; below or behind this towards the middle line a very small tooth, the tip only of which is seen. Male 5 mm. average. Lobes of bursa almost as long as broad, strongly projecting towards the ventral side. Rays short and relatively thick. Female 7 mm.

_Habitat._--Intestine civet cat (_Viverricula malacensis_), Ceylon, and man in Bengal according to Clayton-Lane.

Other species are: _A. caninum_ (Ercolani), in cat and dog, Europe and Africa; _A. malayanum_ (Alessandrini), 1905, in the Malay bear (_Helaretos malayanus_); _A. pluridentatum_ (Alessandrini), 1905, in _Felis mitis_, Brazil.

*Ancylostoma braziliense*, Gomez de Faria, 1910.

In cats (and dog), Brazil. Female 8·5 mm., male 7·5 mm. long. Eggs 65 µ by 32 µ. Leiper considers it to be identical with _A. ceylanicum_.

Group. *Bunostomeæ*, Railliet and Henry, 1909.

Bursa with median double, postero- and postero-external arising from a common trunk, posterior bifurcated, each limb bidigitate (fig. 336). Vulva in middle of body or a little in front. Uteri divergent.

Contains the following genera: (1) Bunostomum (= Monodontus); (2) Necator; (3) Bathmostomum; (4) Gaigeria.

Genus. *Necator*, Stiles, 1903.

Mouth capsule small, narrowed anteriorly (ventrally) by chitinous plates, as in Uncinaria. On each side of the base of the dorsal cone a lateral chitinous plate or lancet with smooth edge (not serrated), ventral lancets as in Ancylostoma. No ridges on outside of ventral wall. Aperture of dorsal œsophageal gland on tip of a cone projecting freely into the buccal capsule. Bursa closed. Posterior ray cleft to its root.

*Necator americanus*, Stiles, 1902.

Syn.: _N. africanus_, Harrison, 1910.

Male 8 mm. long, female 10 mm. The head is strongly bent dorsalwards so that almost by this character alone it can be distinguished from _Ancylostoma duodenale_. The buccal capsule is markedly small--in the male, 0·093 by 0·084 mm., in the female 0·11 by 0·097 mm. There are no teeth anteriorly on the ventral side of the capsule, but instead there are two cutting chitinous plates, the anterior portions of which are prominent and angular, and meet in the middle line in front. Posteriorly on each side the plate projects less, while between the anterior and posterior parts there is a deep angle. The inner (posterior) ventral lancets which also occur in _A. duodenale_ are large, and project far into the lumen, the tips of these, of the lateral lancets, and of the dorsal cone almost meeting in the centre of the lumen. As already stated in the definition of the genus Necator, there are also lateral lancets which start from the base of the dorsal cone. This dorsal ridge, or rather in this case cone, is a striking object in the mouth, and projects right out into the cavity, and on its summit opens the dorsal œsophageal gland.

The bursa is about as long as broad, but has the lateral lobes strikingly lengthened, giving a trilobed appearance (fig. 336), but as in _Ancylostoma duodenale_ it is closed on the ventral side. The distribution of the rays is best understood from the figure. The genital aperture lies on a marked conical protuberance; the cement gland is bilobed in transverse section. In the female the opening of the vulva is in front of the middle line, in _A. duodenale_ it is behind.

The spicules, 0·92 mm. long are hooked at the extremity.

Eggs more pointed at the poles than those of _A. duodenale_, 64 µ to 72 µ by 36 µ, so that it may not be possible to distinguish single eggs owing to individual variations, yet on comparing a number they can be distinguished.

_Geographical Distribution._--Brazil, Porto Rico, Cuba, Central Africa, East Africa, Victoria Nyanza, Gold Coast, Uganda, North-Western Rhodesia, Ceylon, Mysore. For other localities where _A. duodenale_ is also found see p. 450.

_Habitat._--In small intestine of man and gorilla (_Troglodytes gorilla_).

*Necator exilidens*, Cummins, 1912.

Syn.: _N. africanus_, Looss, 1911.

Male 7 mm., female 9 mm. long. The edges of the cutting plates are rounded, not angular, and do not meet in the middle line. Inner (posterior) ventral lancets very small. Lateral lobes of bursa broader than long. Rays thick and plump.

_Habitat._--In the chimpanzee (_Anthropopithecus troglodytes_).

ANCYLOSTOMIASIS.

_Morbid Anatomy._--Organs pale and bloodless. Abdominal organs sodden, and there is fluid in the serous cavities. Lungs: œdema. Kidneys: fatty changes, especially large pale kidney. Liver and heart also show fatty changes--there is much hæmosiderin in the liver cells. Blood: early stages, a leucocytosis 20,000 upwards, and eosinophilia 50 per cent. Later, anæmia (hydræmia). The number of worms found varies from ten to 1,000. They are rare in the duodenum, but occur as far as 6 ft. from the pylorus.

Group. *Syngameæ*, Railliet and Henry, 1909.

Bursa with anterior and median ray cleft; antero-external, close to median; postero-external, arising separately from posterior; posterior bifurcate to base, each branch bifurcate or trifurcate. Vulva in the anterior fourth of body. Uteri divergent.

Genus. *Syngamus*, von Siebold, 1836.

Head thickened, not tapering; broad mouth with gaping buccal capsule.

Male and female often in permanent copulâ.

Parasitic in respiratory passages of birds and mammals.

_Habitat._--_S. trachealis_ in poultry; _S. bronchialis_ in goose; _S. laryngeus_ in cattle; _S. vasicola_ in goats, etc.

*Syngamus kingi*, Leiper, 1913.

Buccal capsules of male and female on same level. In _S. trachealis_ and _S. laryngeus_, that of male in front of that of female. In _S. dispar_, that of male behind that of female. Œsophagus of male one-sixth, that of female one-ninth of total length. Mouth capsule in male and female terminal; it is dorsal in _S. trachealis_ and in mammalian species. Tail of female bluntly pointed. Ovary reaches to anus. Excretory pore opposite the middle of the bulb of œsophagus. In _S. trachealis_ it is opposite the œsophageal valves.

_Habitat._--Found in sputum of patient by King in St. Lucia. Normal host probably a carnivore.

Family. *Physalopteridæ.*

Genus. *Physaloptera*, Rudolphi, 1819.

Mouth surrounded by _two_ large lateral lips bounded posteriorly by a cuticular band projecting anteriorly, forming a collar. Each lip bears anteriorly and inwardly a cuticular appendage, the external tooth. Immediately below and internal to the external teeth the internal teeth, one on each lip. Each lip bears two large submedian papillæ. Tail of male with four pairs of pedunculated papillæ in a row on each side external to the six pairs of unpedunculated papillæ. Spicules unequal. Vulva in the anterior region of the body. Eggs with a characteristic thick smooth shell.

Parasitic in the intestine, more especially the stomach, of mammals (twenty species), birds (twelve species), reptiles (fourteen species).

*Physaloptera caucasica*, v. Linstow, 1902.

The male measures 14·2 mm. in length and 0·71 mm. in breadth; the bursa is broad, rounded off in front and narrower at the back; the right spicule measures 0·62 mm. in length, the left spicule 1·76 mm.; there are two papillæ in front of the orifice of the cloaca, four behind it and six unpedunculated on the tail. The female measures 27 mm. in length, 1·14 mm. in breadth; the caudal extremity is rounded off; the vulva is on the border of the first and second sixth of the length of the body; the eggs have thick shells, and measure 57 µ by 39 µ. It has hitherto only been observed once, by Ménétriés in the intestine of man (Caucasus).

*Physaloptera mordens*, Leiper, 1907.

Large worms resembling an immature _Ascaris lumbricoides_.

The inner lancet-shaped teeth have a sharp cutting edge towards the lumen. Below each is a cuticular boss projecting into the mouth (fig. 340).

Male 30 to 50 mm., bursa with four pairs of pedunculated papillæ, the second and third lying external to the first and fourth on each side. Spicules unequal, one slender (4·6 mm.), the other stouter (6 mm.).

Female 40 to 55 mm. Tail sharp. Vulva opens between the anterior fourth and fifth of the body. Eggs 43·6 µ by 35·3 µ with a thick smooth shell.

_Habitat._--Œsophagus, stomach, small intestine of man (several cases). Nyasaland and Portuguese East Africa.

Family. *Ascaridæ*, Cobbold, 1864.

Sub-family. *Ascarinæ.*

Without œsophageal or intestinal diverticula; spicules without flanges.

Genus. *Ascaris*, L., 1758.

Intermediate lips and auricles absent. Lips edged with fine teeth.
Lips triangular in cross section. Not grooved on internal surface.

*Ascaris lumbricoides*, L., 1758.

The colouring, in the fresh condition, is reddish-yellow or greyish-yellow; the body is of an elongated spindle shape. The oral papillæ are finely toothed. The dorsal papilla carries two sensory papillæ, the two ventral papillæ each one sensory papilla. The male measures from 15 to 17 to 25 cm. in length, and about 3 mm. in diameter; the posterior extremity is conical and bent hook-like ventrally; the spicules measure 2 mm. in length, are curved, and somewhat broadened at their free end; on each side around the orifice of the cloaca there are seventy to seventy-five papillæ, of which seven pairs are post-anal. The testicular tube is much folded, showing through the body integument, and is about eight times the length of the body. The female measures 20 to 25 to 40 cm. in length and about 5 mm. in diameter; the posterior extremity is conical and straight. The vulva is at the junction of the anterior and middle thirds of the body, which, at this point, has a slight ring-like constriction; the convoluted ovaries measure ten times the length of the body.

The ova are elliptical with a thick (4 µ) transparent shell (fig. 342) and an external albuminous coating which forms protuberances; the ova measure 50 µ to 70 µ in length, 40 µ to 50 µ in breadth; they are deposited _before_ segmentation; the albuminous coating is stained yellow by the colouring matter of the fæces, but is sometimes absent. The egg cell is unsegmented, it almost completely fills the shell, and its nucleus is concealed by the large amount of coarse yolk granules.

Abnormal or unfertilized eggs also occur in fæces. They are distinguished by their elongated form (80 µ by 45 µ), irregularly cylindrical, its contents consisting of refractive granules.

_Ascaris lumbricoides_ is one of the most frequent parasites of man; it is distributed all over the inhabited parts of the world, and though it is particularly frequent in the warmer regions, yet it also occurs in Finland, Greenland, etc. In temperate climates _A. lumbricoides_ occurs most frequently in young children; it is, moreover, more common amongst country dwellers than amongst the inhabitants of towns, but is not lacking in infants, adults and aged persons. As a rule only a few specimens are present in the intestine, but many cases are known in temperate zones in which several hundreds of worms have been found in the same patient. This species is particularly numerous in the negroes of Africa and America. It occurs also in the monkey, dog and pig (? _A. suilla_).

The parasite was known in ancient times; the Greeks called it ἐλμινς στρογγύλη, Plinius termed it _Tinea rotunda_, later on it was named _Lumbricus teres_. The ἄσκαρις of the Greeks is our Oxyuris.

The small intestine is the normal habitat of _Ascaris lumbricoides_;
the worms, however, often leave this part of the intestine and wander
into the stomach, whence they are frequently evacuated by vomiting,
or they may creep through the œsophagus into the pharynx and crawl
out through the nose or mouth; very rarely they may find their way
into the Eustachian tube or into the naso-lachrymal duct, or into
the excretory ducts of the liver and pancreas; exceptionally they
may gain the trachea, and they have also been found in the abdominal
cavity. They may bore through adhesions between the intestinal wall
and the omentum (worm abscess); they occasionally penetrate the
urinary apparatus and are passed with the urine; in febrile diseases
_A. lumbricoides_ usually leaves the intestine spontaneously. It is
obvious that these wanderings may be accompanied by the most serious
symptoms, but in sensitive persons the invasion of even only a few
intestinal Ascarides gives rise to a series of almost inexplicable
symptoms (hysterical, epileptiform attacks, cerebral congestion,
aphonia, etc.), which cease with the expulsion of the worms, so
that many authors are driven to the conclusion that these Ascarides
secrete a toxin. Fortunately, the presence of _A. lumbricoides_ in
the intestine is easily demonstrated by the microscopical examination
of the fæces.