Etiology. 



489 



by Looss and the careful investigations of Sticker, published 

 somewhat later (1901). 



The following three species belong to the genus Sclerostomum : 



1. Sclerostomum equinum, Miiller (Strongylos armatus, Rudolph; Str. iieglec- 

 tus Poeppel, Scl. quadridentatum, Sticker). The male is on an average 35 mm. 

 long, 1.25 mm. thick; the female 45 to 47 mm. long and 2.25 mm. thick. Mouth 

 capsule almost regularly long-ellipsoid, with 4 high narrow teeth below them, the 

 dorsal ones densely crowded, the ventral ones separated. The Inirsa at the tail end 

 of the male wider than long, the median flap developed to a lesser degree. The 

 genital pore of the female about 14 mm. in front of the caudal end. Ova oval, thin 

 Bhelled, 65 to 80 ix. long by 45 to 50 n wide. Larvae 0.58 to 0.88 mm. long, similar 

 to those of Scl. edentatum only shorter; its anterior end somewhat conically pointed 

 (Albrecht). 



2. Sclerostomum vulgare, Looss (Strong, arm., Rudolph; Scl. bidentatum, 

 Sticker) claimed to be a young form of the preceding one by Rudolph; however, 

 really a new species, the larvte of which are concerned in the production of so- 

 called worm aneurysm (see page 393). Male at the utmost 15 or 16 mm. long and 

 fairly uniformly 0.7 mm. thick; female 23 or 24 mm. long and 1 mm. thick, 

 slender towards the tail end, mouth capsule like a shallow goblet. Two teeth at the 

 lower end of the dorsal depression of the mouth capsule; these protrude as ear-like 

 projections. Bursa of the male with three flaps, the median one, larger than that 

 of the preceding species, is overlapped by the lateral flaps. The female genital pore 

 8 mm. anterior to the caudal end. Ova 70 to 80 ix long and 43 to 52 /x wide. The 

 anterior end of the larvas (0.7 mm. long) is somewhat rounded off, the posterior 

 portion gradually diminished into a filiform tail end, which is about one-half 

 ehorter than the body. Around the gut 32 larger cells are usually arranged in 

 double rows in mosaic form; the sexual apparatus is situated on a level with the 13th 

 inteBtinal cell (Albrecht). 



3. Sclerostomum edentatum, Looss (Scl. edentatum, Sticker). Length of 

 male 23 to 25 mm., greatest thickness about 1.5 mm.; length of female 33 to 36 mm., 

 thickness about 2 mm. Head 



globular, distinct from 

 body; mouth capsule gob- 

 let-like, teeth-like forma- 

 tions totally absent; how- 

 ever, at the place where 

 the ventral teeth are situ- 

 ated in Scl. equinum, there 

 are some small nodular ele- 

 vations. Bursa of the male 

 very similar to that of Scl. 

 equinum. Genital pore of 

 female 9 to 10 mm. anter- 

 ior to the caudal end. Ova 

 (Fig. 61) 65 to 88 ix long 

 and 45 to 50 ix wide. Larvae 

 0.55 to 0.88 mm. long, body 

 almost one-third longer 

 than the gradually taper- 

 ing caudal end; marking 



of the intestinal cells indistinct, thickness of the body less than that of larvjE of 

 Scl. vulgare (Albrecht). 



P'ig. 61. Ovum of 



Sclerostomum 



edentatum. 



Fig. 62. Ova of Cyathostomum 



tetracanthum. on the right side 



ovum with embryo from horse 



manure ])reserved one day. 



Of the genus Cyathostomum, the most important species is the 

 one generally designated as sclerostomum tetracanthum or strong, 

 tetracanthus : 



Cyathostomum tetracanthum (Strongylus tetracanthus Mehlis, Sclerostomum 

 tetracanthum), white worm; male about 9 mm., female 10 to 12 mm. long. Mouth cap- 

 sule fairly shallow, narrowed in the middle, fine triangular leaflets, arranged in a 

 radial manner and looking from above like a wreath of fine bristles (called by Looss 

 internal leaf wreath) spring from the narrowed place of the mouth capsule. In 

 front of the anterior margin of the mouth capsule there is an outward projecting 



