Roundwoniis. 475 



C. Roundworms. Nemathelminthes. 



The body of rouiKhvorms is elongated, cylindrical and not 

 segmented. Thread worms (nematodes) and Acanthocexjhahi 

 occur in domestic animals. Both are differentiated into separate 

 sexes. The thread worms are generally provided with a well 

 developed intestinal canal, which opens with two stomata at the 

 surface of the body; Acanthocephala have no intestinal canal 

 and the anterior end is formed by a protrusible proboscis, pro- 

 vided with hooks. 



(a) Ascaris in Mammals. Ascariasis. 



Occurrence. Ascaris and affections produced by them are 

 frequently seen in young animals ; older animals are more rare- 

 ly affected and then generally only by few worms of this type. 

 Animals which can run around free in the l)arn or on the pas- 

 ture are especially exposed to infection, while animals which 

 are tied can more rarely find a chance to take up the ova 

 of ascaris (Albrecht). Enzootics have been observed among 

 calves of 3 to 5 months (Leibenger, Gasteiger), among young 

 pigs, occasionally among lambs (Vallisneri), foals, also among 

 dogs. 



Etiology. Roundworms are long, smooth cylindrical 

 worms, with a short head and with three lips, either smooth or 

 armed witli teeth around the mouth. 



The following worms occur in domestic mammals : 



Ascaris megalocephala, wliite or yellowish white, rigid worm ; its three 



1. Ascaris megalocephala, white or yellowish white, rigid worm ; its three 

 mouth-lips are ]irovided with teeth, made 15 to 28 cm. long, its posterior end conical 

 with two skin-like small wings, directed towards the ab- ^f0KSaiit^ 



dominal surface; the female 18 to 37 cm. long, its hind 

 end blunt, straight ; the sexual pore is at the anterior por 

 tion of the body. Ova globular or somewhat elongated 

 oval, in the feces of the host usually yellowish-])rown, not 

 segmented or only in the first segmentation stage; diame- 

 ter 90 to 100 /JL, surface smooth (fig. 55). The worm lives 

 in the small intestine of the horse and, according to Sehim- 

 ir.elpfennig, the mature individuals also suck blood. 



2. Ascaris vituli, with reddish-white translucent body. 

 Male 15 to 20 cm., female 22 to P.O em. long, genital poi'o Fig. 55. Ovum of As- 

 in the anterior sixth of the body. The diameter of the carls megalocephala. 

 ova is 75 to 80 fi, the membrane ajijiears finely wavy. The 



worm lives in the small intestine, exceptionally also in the abomasum of calves; it is 

 rarely found in adult cattle (Clasteigor believes that the roundworms which he found 

 in calves were Ascaris lumbricoides). 



3. Ascaris ovis, yellowish-white worm, mouth-lips provided with teeth ; male 

 7 to 10, female 7 to 12 cm. long. Very rarely found in the intestine of the sheep. 



4. Ascaris lumbricoides (ascaris suilla), body white or pale reddish, mouth 

 lips provided with teeth. Male 15 to 17 cm., female 20 to 25 cm. long; the anterior 

 end of the male is bent like a hook, that of the female straight; the female genital 



