44 r>E. T. S. COBBOL-D ON TEEMATODE PARASITES 



new and peculiarly modified intermediary bearers, but also in other 

 ways to alter materially the conditions of existence. "Without a 

 doubt some fluke-parasites are confined to particular localities ; 

 and this is solely due to the fact that their bearers and interme- 

 diary bearers are alike restricted to a limited territory. But for 

 these restrictions, there is good reason to fear that (as in the case 

 of Bilharzia, for example) several of the most terrible endemic 

 disorders, now confined to limited areas, would become world- 

 wide. Fortunately for them, the lower animals are much more 

 capable of resisting the untoward effects of parasitism than our- 

 selves. "We, however, have the power of warding off most of the 

 dangers from this source, since we are now in a position to adopt 

 preventive measures. This is entriely due to the advance of 

 helminthology. As regards domesticated animals, it may pro- 

 bably be said with truth that they suffer from entozoa more than 

 wild ones. In the course of a large experience, however, I cannot 

 say that I have found wild animals very miich less infested. With 

 the multiplication of beasts of burden and other serviceable quad- 

 rupeds there have also arisen greater facilities for infection ; and 

 if, as unfortunately seems to be the case, parasitism amongst do- 

 mestic animals has increased rather than diminished, it is because 

 those who possess the power to put a check upon these disorders 

 have not thought it worth their while to obtain special informa- 

 tion on this head. 



As regards wild animals, it is well nigh impossible to acquire 

 correct data as to the destructiveness of parasites. I have no he- 

 sitation in saying that half the amount of parasitism that I found 

 in Mr. Murray's porpoise would have killed any ordinary domesti- 

 cated animal. Our cattle and sheep are carried ofi' by thousands by 

 much less formidable lung-parasites than that cetacean harboured. 

 Doubtless wild animals, cetaceans amongst them, becoming at 

 length weakened by their parasitic guests, more readily succumb to 

 their various other enemies, which, in the struggle for existence, 

 are only too ready to reap the desired advantage. On the other 

 hand, I have little doubt that the porpoises and seals that have 

 died at tbe Zoological Grardens, and whose lungs were largely in- 

 fested by parasites, would, in their natural haunts, have borne up 

 against the evil effects of a much larger amount of parasitism than 

 they were enabled to do in confinement. One conclusion, at all 

 events, is inevitable, namely that endemics, epidemics, or epizootics 

 of the parasitic kind, call them what we may, are for the most part 



