16'2 WOKMS INFESTING THE DOG. 



their way into the intestines of the unborn whelp is beyond my 

 knowledge, as it is not supposed that in any stage either the 

 Ascaris or the Oxyuris have any boring apparatus, like the embryo 

 of the Tcenia. It is true, as we shall presently see, that the latter 

 often wanders in its mature state from the rectum of the animal 

 which bred it, and it is very possible that it might in this way 

 reach that of any other dog, supposing the latter has left the 

 uterus and been born. But as we know that the foetal animal is 

 invested by a membranous covering while in the uterus, this 

 would not explain the appearance of the maw-worm if found in it ; 

 and, moreover, the only worms I have ever known or heard of 

 being found in the newly-born puppy, are the Tcenia cucumerina 

 and the Ascaris marginata. We know, however, that embryo 

 entozoa are in some way transferred from the internal surface of 

 the stomach to the interior of the blood-vessels, and through them 

 conveyed to their proper nidus. It is, therefore, equally possible 

 that the nematoid worms may in this way reach the circulation of 

 the mother, and thence pass to that of the foetus, but even then 

 they would have again to be transferred to the intestine of the 

 latter. The subject is one very difficult of comprehension, and in 

 our present state of ignorance we can only say that we know 

 nothing about it except on the most vague hypothesis. 



I shall now proceed to describe the appearance and habits of 

 the two round-worms which infest the dog so commonly as to 

 make their presence almost the rule rather than the exception. 

 M. Davaine enumerates three others, namely, Holostomum alatum, 

 Trichocephalus depressiusculus, and Dochmius trigonocephalus ; 



