PARASITES OP ANIMALS. 327 



it under different heads, grouping together those animals 

 ■which harbor the same species of worm. 



Verminous bronchitis in the ox, horse, ass, and mule. — The 

 same parasite attacks one and all of these animals. This is 

 the Strongylus micurus of Mehlis, a small, thread-like worm, 

 the male one and a half inches long, the female three inches. 

 The head is rounded, with no constriction or neck, the mouth 

 furnished with three chitinous papillae, the oesophagus club- 

 shaped, the genital orifice of the female situated in the ante- 

 rior half of the body, and the tail pointed : the male has a 

 caudal pouch with five rays standing well apart. They were 

 noticed by Camper to be viviparous, but this must be qualified 

 by the statement thq,t the female, after becoming imbedded in 

 the lung substance, or after being expelled by coughing, per- 

 ishes often with its oviducts still full of ova, and these gradu- 

 ally hatch out amidst the decomposing debris of the parent. 



Development. — The development of the parasites has to be 

 considered as it takes place in and out of the body. Within 

 the body in the earlier stages of their life — that of ova and 

 embryos — the parasites are found imbedded in the substance 

 of the lung-tissue, mostly toward the margins of the lobules, 

 where they may live for indefinite but often long periods. 

 Baillet killed a lamb thirty -two days after he had administered 

 the embryos of a Strongylus filaria taken from the oviducts of 

 a female worm, and found the parasites rolled up into pellets 

 in minute semivitreous nodules in the posterior part of the 

 lungs, and varying in length from one-third to a line. It is prob- 

 able, therefore, that these lung-infesting strongyli may live for 

 many months encysted in the pulmonary tissue in this imperfect 

 condition. The appearance of the lung so affected is redder 

 than natural, and its surface feels rough and uneven by rea- 

 son of the numerous exudations around the embryo worms. 

 These nodules, which were long mistaken for miliary tuber- 

 cles, vary in size from that of a pin's head to that of a barley 

 corn, while at certain points many will become accumulated 

 so as to cause uniform consolidation of lung-tissue to a con- 

 siderable extent. They vary, too, in consistency from a sim- 

 ple semifluid mass to a hard calcareous shell. The soft and 



