41 G THE MODERN HORSE DOCTOR. 



shaded. The skin itself is translucid and vesiculous, as it were. 

 In size, the larva is much below the hypoderma bovis, since it 

 does not exceed an inch in length, while the larva of the ox 

 oestrus, at full growth, attains to from three to four inches. 



" This difference, in itself considerable, is not the only one we 

 have to remark. Upon the subject of our inquiry we do not ob- 

 serve the six longitudinal lines which, upon the hypoderme of 

 the ox, form so many series of tuberculous eminences, ranged at 

 certain intervals from the first to the last segment. Neither are 

 to be seen the five or six eminences surrounding the mouth of 

 the latter ; though, to make up for it, we find at the posterior 

 and inferior side of the second segment a kind of transverse 

 prominence shooting beyond the surrounding skin, and furnished 

 with very small tubercles, which have no existence in the grub 

 found in the skin of the ox. 



" These differences, united to those of size, suffice, in our mind, 

 to authorize the conclusion, that the larva in question, though it 

 belong to the genus hypoderma, constitutes a distinct species, up 

 to the present time undescribed, to which we shall give the name 

 of hypoderma equi. 



" No doubt we shall be asked, What are the habits of this in- 

 sect in its different states ? Nobody, as yet, that we know of, 

 has investigated them. The larva alone being recognized, it is 

 to that the few observations apply of which science is in posses- 

 sion. We know that this larva is found principally upon horses 

 that have been living at pasture in the months of July and Au- 

 gust, and that through its presence are caused large indurated 

 knots or buttons upon the skin, which are found in the greatest 

 numbers along the spine, from the withers to the croup inclusive. 

 These buttons, whose volume varies from a lentil to a small nut, 

 have, according to M. Loiset, a shape inclining to conical ; and, 

 by carefully separating the hairs clothing them, may be seen on 

 their summit a narrow aperture, resembling such as a large 

 needle would make. Compressing the tumor causes to issue 

 from this opening a minute quantity of purulent serosity, which, 

 after being removed, is followed, in the last months of the growth 

 of the tumor, by a vesicular point, which is neither more nor less 

 than the posterior extremity of the larva. The efforts made to 



