OCR Text |
Show 1905.] IX A CASTRATED PRONGBUCK. 193 variations described below to be due to castration, it is evident that the operation has affected the horns in a very remarkable manner. Description of the Horns. Instead of rising from the forehead as upright, laterally-com pressed, bony prominences, the horn-cores bend obliquely forwards in a vertical plane, their axes inclining to the plane of the forehead at an angle of about 45°. They are only about 2 inches long. The horn-sheaths cover the core to the root, becoming gradually softer proximally, and passing into the hairy integument of the head. They project nearly horizontally forwards in the direction of the nose for a distance of about 3| inches, then curve downwards for about 2| inches, and then backwards towards the eye for about 3? inches, the terminal inch curving lightly inwards and downwards to a point close to the eye. Their total length along the outer or convex curve is thus about 9^ inches. They also present a spiral twist forming about one-fourth of a complete turn. This is attested by the fact that an interfibrous groove starting in the middle line of what is morphologically the posterior surface of the base, but which by the change in the direction of growth has become secondarily the upper or dorsal surface of the horn, gradually passes on to its inner surface to terminate on the concave side of the apically curved portion, this concave area being also, morphologically, although it faces the middle line, part of the posterior surface of the horn, as is abundantly proved by the recurvature of the apex of the normally formed horn. The same extent of torsion is further shown by the lateral compression of the base of the horn being replaced by dorso-ventral compression towards the apex, the normal horn being laterally compressed throughout. Briefly stated, the result of the twist is to make the distal half of the posterior surface of the horn face the middle line of the body. Although the horn-sheaths have been described above as if each corresponded to a single fully-formed horn-sheath of an adult Prongbuck, closer examination shows that they are in reality composite-that is to say, they consist of a series of horn-sheaths partially severed from each other. The exact number of sheaths involved in the formation of the whole is not easy to determine. There appear, however, to be six. In the right sheath, the outer or convex side shows a continuous and unbroken surface except at two points, the proximal break occurring at about | of an inch from the base, and the distal a little more than 2j inches from the apex ; there is, however, a partial break inches behind the distal break. These three breaks arecontinued round the horn on to its convex side, and very evidently represent the proximal ends, formerly extending to the root of the horn-core, of three separate sheaths. Moreover, on the concave side there are two additional breaks in the continuity of the tissue which extend only half round the sheath, one situated at about 1 1 inches |