2 THE INTERNAL PARASITES OF 



the measure of his admiration of the phenomena of 

 parasitism by frankly saying : ' ' In the life-history of 

 these creatures you are dealing with one of the most 

 interesting and suggestive problems which physiology 

 presents, and you are at the same time contributing to the 

 accomplishment of a task which promises a boon to the 

 human race scarcely second to that conferred by Jenner." 

 He might, perhaps, have appropriately added : If the 

 brute creation could understand and speak, it would, on 

 knowing the ultimate results of the labours of helmin- 

 thologists, also audibly render its grateful homage. 



I shall introduce the subject by some general observa- 

 tions respecting the parasites of the ox. 



The ox, considered as a supporter or bearer of parasites, 

 is, like all other animals holding a similar relation, tech- 

 nically and very conveniently termed a host. As such he 

 is liable to entertain a great variety of entozoa; and he 

 is frequently also the victim of injurious attacks by 

 several species of insects, which are not entozoa in the 

 zoological sense, though some of them are undoubtedly 

 so in the more general acceptation of that term. Certain 

 of these insects are parasitic both in the adult and larval 

 conditions. The ox, moreover, is the bearer of the 

 juvenile stage of development' of an important human 

 parasite ; and within the tissues of its body — as obtains 

 also in the case of other food-producing ruminants — we 

 may encounter a multitude of those minute parasitic 

 organisms erroneously called " cattle-plague " bodies. 



It would carry me beyond the aim and scope of the 

 present work to give any particular account of these 

 singular organisms; the more so, since they neither 

 belong to the helminths or intestinal worms (as some 

 prefer to call them) , nor are they capable of producing 



