490 Worms in the Intestinal Tract. 



wall formed bv the skin, this wall is likewise provided with radially arranged leaflets 

 (external wreath of leaves). Sexual pore at the posterior end, directly in front of the 

 anus; ova (tig. 62) oval 90 to IIU fi long, 40 to 50 /x wide. The e-audal end of the 

 larva; (0.46 to O.SO nun.) is about one-third longer than the liody proper, anterior 

 end of the latter somewhat more pointed, the union of the body proper and the tail 

 end well marked ; the intestinal tract only shows 8 or 9 larger alternating cells, on a 

 level with the fifth of these cells the sexual apparatus is situated (Albrecht). 



As the representative of a third genus Looss distinguishes Triodontus which has 

 an almost globular small but thick-walled mouth capsule, which possesses no real 

 teeth, but the chitinous lining of the three-cornered lumen forms three projecting 

 toothdike formations. The genital pore of the female is situated near the caudal 

 end. Two species belong to this genus: Triodontus minor and Triodontus serratus. 

 They do not, however, appear to occur in Europe. 



According to Leiickart, Cobbold and A. Albrecht, the develop- 

 ment of Sclerostoniuui and of Cyathostomuni tetracanthum is as fol- 

 lows : In the ova, which are voided with the feces of the host, em- 

 bryos develop in the outside world, under favorable conditions of 

 temperature, in 3 to 4 days, later in winter, which after hatching, be- 

 come larva? 0.4 to 0.8 mm. long, round with filiform, caudal ends. In 

 water or in dry dust, the larvae can live only a few days, but they may 

 remain alive for months in moist or at least not too dry horse manure. 

 After 15 to 20 days, or at a temperature of 30° C, shedding takes place 

 in a few days; the detached cuticle is completely shed, however, only 

 after several months. With this shedding, the resistance of the larvae is 

 much increased, and it may now not merely survive in horse manure 

 for several months, but also in pure water for 6 to 8 months, and it is 

 not even killed at freezing temperature (0° C). The hatched em- 

 bryos probably go through three or four moults, although Albrecht 

 observed only one shedding. After slipping out of the shell, the larvfe 

 lose their whiplike tail end and they are frequently designated as rhab- 

 ditis forms. 



The ingestion of larvae occurs wdth contaminated drinking 

 water, with feed contaminated wdth manure or on infected 

 pastures. The infection is not confined to certain seasons as was 

 assumed by Sticker. 



The views of authors differ as to the further fate of the ingested larvae. Ac- 

 cording to the views of Leuckart, Eailliet, Sticker, Glage, the larvae bore into the 

 intestinal wall immediately after ingestion, get into the general circulation and 

 are transported to various organs. Larvte of Scl. bidentatum then settle in certain 

 arteries (see page 393) from Avhere they are washed away after several weeks or 

 months (Glage) ; they then remain for several weeks in small no<lules of the intes- 

 tines (especially in the cecum. Sticker), then they get again into the intestinal 

 lumen where they now copulate. Larva? of Scl. edentatum from the abdominal 

 organs get into the intestine by active wandering (Glage, Schlegel) and they pro- 

 duce mechanical lesions in these organs. According to another view (Colin, Willach, 

 Olt), larva? found in the blood vessels and other organs are only looked upon as 

 individuals that have gone astray and that can no more contribute to the preserva- 

 tion of the species. 



Anatomical Changes. No changes are noticeable in the 

 mucosa of the large intestine in the presence of mature indi- 

 viduals of Sclerostomum qnadridentatnm and Sclerostoma 

 l)identatum, but the larvji^ of 8cl. bidentatum produce thrombo- 

 sis, particularly in the mesenteric arteries (see^page 393). Cya- 

 thostomum tetracanthum may cause hemorrhagic inflammation 

 of the large intestine. In acute cases of sclerostomiasis caused 

 liy tlie hirv:r of Sclerostoma edentatum one finds a purely serous. 



