182 



The life history of this species has been determined by Leuckart, the 

 distinguished helminthologist, who has added so much to this branch of 

 biology. He succeeded in raising young embryos ftom the eggs to such 

 a stage that there was no reasonable doubt that the next stage was passed 

 in sheep. These he fed to a lamb, which he killed after sixteen days. 

 In these he found numerous immature trichoce^hali a.hontl'"'^ in length. 

 He later verified this experiment by another, with like results. (Die 

 menschlicheii Parasiten, Band II, 494-499.) 



These experiments show that the eggs of Trichocephalus affinis, which 

 pass from sheep to the ground, may develop there to some degree, and 

 then, after being consumed with food or drink by a second sheep, con- 

 tinue their development to their adult stages. 



Disease and treatment. — Unless the parasite should be present in great 

 abundance the species does not seem to be especially harmful. A few 

 may be found in nearly all lambs and young sheep, especially in the 

 all. The means of prevention is just the same as for other round 

 worms. As they are attached so stoutly to the mucous membrane it is 

 doubtful whether medicinal remedies would have the influence on them 

 that they have on those worms situated in the small intestine. 



