IMMATURE TAPE-WORMS-BLADDER-WORMS. 



Plates IX, X, and XI. 



Besides the adult tape-worms found in the intestines of sheep, there 

 have been four other species described which infest various portions of 

 these animals in their immature stages. These species are Tcenia mar- 

 ginata, Batsch, T. coenurus, Kiich., T. echinococcus, v. Siebold, and T. 

 tenella, Cobbold. The forms found in sheep were first described as 

 Gysticerci, and have since been known as Cysticercus tenuicollis, Coenurus 

 verebralis, Echinococcus and Cysticercus ovis, respectively. 



All these species resemble each other in their anatomical structure, 

 their growth, and their life history. They differ in minute structure, in 

 invading different portions of the sheep, and in the effects they produce 

 on the animal, 



Twnia marginata is more common in the United States, and T. coenurus 

 next. iN'either of the other two species have beeu found in sheep in this 

 country. 



TjEnia marginata, Batsch. 



Plate IX. 



Tcenia marginata occurs in sheep as a little semi-transparent bladder 

 filled with liquid, varying from a very minute size to a bag an inch or 

 more in diameter, but usually having a diameter of a half or three- 

 quarters of an inch. 



Occurrence. — This tcenia, in its cysticercal stage, is usually found be- 

 tween the layers of the serous membrane which form the omentum, or 

 "caul" of the abdominal cavity. It may be found in the liver, espe- 

 cially within a week or two after the infection of the sheep by it. A very 

 common place to find it is between the folds of serous membrane which 

 suspends the intestine iu the pelvic cavity. When one of these little 

 fliildsacs are found it may be cut out, with the surrounding tissue for 

 examination. Afterwards great care should be taken in dissecting the 

 serous tissue, which forms an outer sac, so that the cysticercus within 

 shall not be cut, its contents allowed to escape and its walls to collapse. 



Description of cystic stage. — The smaller bladders are apparently com- 

 posed of a semi translucent whitish membrane, at one end of which may 

 be seen a whitish thickening. As the bladders grow the walls become 

 slightly thicker and the spot at the end becomes much larger and pro- 

 jects in the form of a knob. 



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