NERVOUS SYSTEM AND ORGANS OF THE SENSES. - The general arrangement of the nervous system and structure of the organs of sensation offer in the class before us no peen liarities of sufficient physiological importance to require a detailed description: we append, however, figures representing the cerebral con volutions and the base of the encephalon of the horse for comparison with similar figures given in other articles.
the latter end of June, during which period he will efficiently serve fifteen or eighteen mares.
The scrotum is suspended between the thighs at a distance of about nine inches be neath the anus, whence it is prolonged for wards, to terminate in the prepuce (t. 18.
a, f, e).
The penis (fig. 518. c, d) is full a foot in length even in its undistended state, measur ing from the bifurcation of the corpora caver nosa (b) to the extremity of the glans (c), which latter organ is itself nearly half a foot in length, and four inches in circumference ; its shape is cylindrical, and it is covered with a soft and smooth skin.
OFtGANS OF GENERATION. Male Generative Org,ans.— The external organs of generation in the male solipeds are remarkable for their great development, and in nearly equal pro portion are these animals conspicuous for their vigorous and fruitful generative powers, which, however, are only called into full ac tivity at a certain season of the year, namely, in this climate, from the beginning of April till The testicles (one of which only (g) is repre sented in the figure) are of an ovoid flattened form, each being about three inches long by two inches broad, and one inch and a half thick : the epididymus (h ) issues from its anterior part, and is cotnposed of large tubes of a yellowish colour, bound up together in munerons small bundles. Arrived at the pos terior extremity of the testes, the epididymus folds back upon itself, to constitute the vas deferens ; which, at its commencement, is very tortuous, and forms a protuberance of considerable size (/). The vasa deferentia (l, 711, n) are upwards of fourteen inches in length, and, during the greater part of their course, about two lines in diameter ; but to wards their termination they become, for a length of about seven inches, much dilated, here measuring upwards of fifteen lines in circumference (oo). The caliber of the in
ternal canal does not, however, expand in proportion to tbe dilatation of the exterior of the duct.
Female Organs of Generation.— The gene rative organs in the female solipeds offer no variations of structure from the usual type common to placental quadrupeds. The di tolis (fig. 519. a) is of great size, and is lodged in a cavity appropriated to its recep tion, situated immediately above the inferior (i. e. anterior) commissure of the labia pudendi ; its glans is enclosed in an ample prepuce, above which may be observed an orifice leading into a cavity big enough to lodge a small bean. The canal of the vagina is about a foot in length, and in its capacity corresponds with the ample dimensions of the penis of the other sex.
Immediately behind the orifice of the ure thra, the mucous membrane of the vag,ina forms a broad fold, which is directed forwards and lies immediately over the urethral opening : the length of this fold in the adult mare is about eight inches, and, near its middle, it is upwards of an inch in breadth.
The urinary bladder is small in comparison with the size of the animal ; its shape is nearly round; and its circumference, when moderately distended, about a foot and a half. The urethra is remarkably short and capacious, the circum ference of its canal being about three inches, while its length is only about an inch and a quarter.
The orifice of the uterus (i) projects to the distance of about half an inch into the upper end of the vagina, and is of a rounded shape, encircled by a thick margin. The womb is made up of the body and two cornua, which latter, in the unimpregnated state, measure about seven inches in length.