INTESTINAL WORMS. 153 



present theory of their generation will not suffice. Still there 

 seems to be little doubt of the truth of their natural history 

 under other circumstances, as described by Kiichenmeister and Von 

 Siebold ; and its importance cannot be overrated when we consider 

 that upon it depends the power of preventing the development of 

 intestinal worms altogether. Every experienced courser knows 

 the difficulty of expelling them without injuring the health of the 

 dog, and would appreciate any means likely to lead to their pre- 

 vention in preference to their cure. I shall therefore endeavour 

 to put my readers in possession of the present state of our 

 knowledge on this abstruse subject. 



Though the highest authorities on the generation of parasitic 

 worms are not quite agreed on minute points, yet they all come to 

 nearly the same general conclusions as to their progress from the 

 ova to the fully-developed worms, the most remarkable feature in 

 which is the fact that a great part of it goes on independently of 

 the intestine of the dog. In the Tcenia serrata, and very probably 

 in the Ascaris marginata, if we could isolate the dog from the 

 sources whence these animals are derived, we should altogether 

 prevent their existence in his alimentary canal, but in order to do 

 this it is necessary to ascertain what those sources are, and, as far as 

 I know, that of the Tcenia cucumerina has yet to be ascertained. It 

 appears pretty clear that the heat of boiling water or of the oven 

 will destroy the ova of the parasitic animal in any stage of de- 

 velopment, and thus it is easy to prevent their entrance with the 

 food ; but as worms are often developed in kennels where no un- 

 cooked food is ever given, there must be other sources from which 



