THE MODERN HORSE DOCTOR. 415 



" At the present day, with nature herself before our eyes, we 

 feel satisfied that this description, confessed to be imperfect even 

 by the author himself, viewed as a branch of natural history, is 

 wanting in exactitude. And this induced him to introduce a 

 portrait of the insect in question, with a fresh description of it 

 more in accordance with the rigorous precision prescribed by 

 science. 



" Its character once well established, we shall be able readily 

 to resolve the question, whether the oestrus in point be identical 

 with the hypoderme of the ox, or whether it constitutes another 

 species to be added to the genus hypoderma. 



" The larva cuticolens (skin-habitant grub) of the horse has a 

 cylindrical form, measuring more round in its fore than its hinder 

 part. It is without brain or feet. Its body is constituted of 

 eleven segments, including the one in which is found the buc- 

 cal orifice, (or mouth,) which consists of a very small hole, edged 

 with a black border, with some bristles around so fine as to be 

 with difficulty perceptible by the naked eye. The foremost 

 segment is of all the smallest. From this the segments, as far 

 back as the fifth, grow gradually larger ; while, on the contrary, 

 the five posterior continue to diminish as they approach the 

 hinder part. These segments, examined upon their ventral sur- 

 face, with the exception of the two last, are divided transversely, 

 by slight grooves, into two unequal halves, each furnished with a 

 great number of spinous tubercles, whose points, upon the ante- 

 rior half of the segment, are directed backwards, but forwards 

 upon the posterior half. Two cribriform plates, the sole organ 

 of respiration with which the grub is furnished, are seated upon 

 a sort of flattened termination of the anal segment. 



" Alike in this respect to the hypoderma bovis, the skin-habi- 

 tant grub of the horse has, contrary to what is observed in the 

 majority of cases, the inferior surface of the body convex, while 

 the dorsal side of the segments is slightly concave. Such form is 

 in this manner exactly fitted to the spherical cavity which serves 

 as a habitation for the parasite. It is worthy of remark, that 

 the dorsal surface of the body is without bristles, save upon the 

 two or three foremost segments. The general color of the skin 

 is white ; the bristly tubercles alone being brown, more or less 



