THE STOMACH ROUND WORMS. 

 Steongylus contortus, Eud. 



Plate XVIII. 



Strongylus contortus, or the twisted strougyle, is an inhabitant of the 

 fourth stomach of sheep and goats. Though in the majority of flocks 

 it produci^s but little if any disturbance, yet there are times when, in 

 connection with other species, it causes disease which may carry off 

 numbers of lambs. In the southwestern States and Territories the 

 disease has been called Jom6n«, a corruption of the Spanish word ifo»i6Hci, 

 meaning worms. The later writers seem to be inclined to attach a 

 specific meaning to this word, while the Mexicans, who used it, merely 

 Intended to say that the lambs died of worm disease. 



Description. — Female, 18 to HO""" long; male, 15 to 20™™ long; body reddish; 

 female luarkcd by a double spiral white line, thicker toward the caudal end. The 

 skill shows eighteen longitudinal lines. The mouth is round and without visible lips 

 or papillae. The neck has two barb-like sidepapilhe; unicellular glands scarcely 

 visible. The male is about two-thirds as long as the adult female, and shows no 

 spiral line. Bursa deeply bilobed, with a small dorsal lobe attached to one of the 

 pair. The lobes are somewhat longer than broad. The ventral costse are separated ; 

 the lateral are double and separated ; the dorso-lateral is attached to the lateral group 

 near its base; the dorsal costse support the dorsal lobe and each branch is double; 

 the twofold character is indicated by a little notch. The lateral costse are irregu- 

 larly divided, many variations being observed. Spicula two, embracing a chitinous 

 piece between them. They are short, cylindrical, barbed on one side near the end, 

 and have blunt tips. Female: Vulva 3™™ from the tail and covered by a nipple- 

 like projection, 0.5™™ long; the latter has thin borders, and is concavo-convex, to fit 

 the body when pressed against it. Uteri two, each opening into the common vagina ; 

 one is anteriorly directed and the other posteriorly, with a short loop between it and 

 the vagina. The ovary of the posterior uterus is reflected anteriorly to rejoin its fel- 

 low, and together they wind spirally around the dark-colored intestine. The ovoid 

 eggs are laid in the gastrula form, or after they have passed through the segmenta- 

 tion stage; length, 0.070 to 0.097™™; width, 0.043 to 0.054™™. 



Occurrence. — This worm may be found in all stages in the fourth 

 stomach or abomasum of sheep. When collected immediately after 

 death from a slaughtered sheep they may be detected adhering by their 

 heads to the mucous membrane. They are then of a reddish color, which 

 may be because they feed in part upon the blood of the victim. 



The life history of Strongylus contortus seems to be apparently simple. 

 Among a number of lambs kept at the Experimental Station in 1888 

 were two or three which had been raised there. A post-mortem exaini- 



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