DISEASES OF THE OX AND SHEEP. 431 



mercy. This may be consistent with the advancement of the 

 community, for it may be necessary that the higjher animals shall 

 gain or keep the power of repelling such attacks ; but it cannot 

 be considered as anything but detrimental to the units attacked, 

 when regarded as distinct individuals, and not as members of the 

 ever-advancing aggregate. Indeed, this implication of the great 

 law of evolution must probably be always more or less true ; but 

 as regards mankind the interests of the individual and those of 

 the aggregations will become gradually more and more blended, 

 in proportion as the strong, the powerful, and the wealthy realise 

 the raison d'etre of their advantages, and the best uses to which 

 their strength and power and riches can be put. No matter 

 what men's social distinctions may be, no matter how great their 

 fame, they are all made up of flesh and blood, and nerves and 

 bones, and all are subject to the attacks of parasites of divers 

 kinds and degrees of power to destroy. 



One instance of parasitism in relation to cattle which attracts 

 marked attention, is the disease to which we have already briefly 

 referred. It is popularly known as Husk or Hoose, and more 

 scientifically as Parasitic or Verminous Bronchitis. This malady 

 is, as we have said, somewhat difficult to cure. It often attacks 

 sheep, and, as the latter name implies, it is due to the presence 

 of the worm, called Strongylus micrurus, often in considerable 

 numbers within the air tubes. 



Another example will readily recur to farmers' minds. Espe- 

 cially in hot and sultry days, stock-owners will be glad to hear a 

 little more about the two insects known as the warble-fly and the 

 gad-fly of the ox, notwithstanding that Miss Ormerod, in The 

 Yorkshire Weekly Post of May 14th, 1887, gave a lengthy and 

 valuable description of these pests, and that Mr. John Walker's 

 good little pamphlet on the subject is well known. 



There are other parasites which also demand some attention, 

 and we may mention the liver-fluke, which not only attacks 

 sheep, but also oxen, and indeed many other animals. Tape- 

 worms, in their connection with oxen, must also be briefly con- 

 sidered. The parasites of the skin of oxen do not need much 

 notice, and they will be mentioned under our article on the 

 skin. 



The Warble-fly of the Ox. 



In the month of July the warble-fly is still busy among the 



