PARASITES OF ANIMALS. 129 



and thus pass them with the faeces. In either case they will 

 often adhere to grass *nd other herbage, and may thus be 

 swallowed by other sheep or lambs, fed in the same pastures, 

 and pass directly into the windpipe, or else do so when the 

 cud is raised for mastication. Therefore lambs should never 

 be put into fields or pastures where diseased animals have 

 been kept, but such infected lands should be tilled, or at least 

 left at rest for several months. As soon as an animal gives 

 any indication of the presence of the parasites by the 

 peculiar cough, it should be separated from the rest of the 

 flock for treatment ; or else immediately killed and the para- 

 sites should be effectively destroyed, and not thrown on the 

 ground as harmless, for all these worms are remarkably 

 tenacious of life, and often may even be dried up completely 

 for months, and then revive when moistened. 



Remedies. 



When these parasites are once lodged in numbers in the 

 substance of the lungs, there is probably no reliable remedy 

 whatever. When merely in the windpipe and bronchial tubes, 

 expectorant medicines that will produce a copious secretion 

 of mucus may be useful. It might be possible to remove 

 them by a surgical operation, opening the windpipe from 'the 

 exterior, but this would require surgical skill and would not 

 pay, perhaps, except as a last resort for valuable animals. 



The Strongylus of Cattle and Horses (Strongylus micrurus 



Mehlis). 



This species closely resembles the preceding. The male 

 grows to the length of about one inch and a half ; and the 

 female to three inches or a little more. The body is very 

 slender with a simple, blunt head. The bursa of the male 

 has five rays. The female genital orifice is near the middle 

 of the body. It is said to be viviparous. 



The habits of this species are nearly the same as those of 

 the last, except that this inhabits the air-passages of cattle, 

 horses, asses, and mules, instead of sheep. It is much more 

 liable, like the former, to infest young animals than adults. 

 Calves less than a year old are particularly liable to be in- 

 17 



