In connection with the male organ of generation may be noticed the preputial glands, which, in some of the Rodentia, are very largely developed. This is more espe cially the case with the beaver, in which animal they secrete the drug castoreum, once much used in medicine. These glands form remarkable on account of the prominence and number of the ova which they contain, giving several wide pouches (fig. 284. e, f, g,h, k), situated on each side of the perputial sheath. The structure of these glands is shown in fig. 286. ; they are arranged in two sets, of which the lower, three in number on each side (h, /,o), are found when opened, as represented on the right hand side of the figure, to be hollow, the walls enclosing their central cavity being made up of numerous small glandular masses, that secrete a thick yellowish fluid. The upper set consists of two capacious bags (p), which, when opened, are seen to have their lining membrane (r) deeply rugose. The secretion of these pouches is of a deep grey colour, and, if possible, niore disagreeable.
Female organs of generation. —The ovaria in the female Rodents occupy, the same tion as in other Mammifera, and are chiefly them a somewhat racemose appearance. The
uterus is always deeply divided into two long cornua, and this division is in some cases carried to such an extent that the body of the uterus constitutes but a very insignificant part of this viscus, and is even absolutely wanting, as, for example, in the hare and in the rabbit, in which animals the cornua uteri open separately into the upper part of the vagina, so that the uterus is literally here double, as represented in the appended figure (fig. 287.), where two probes Eh, 0 are introduced into the two distinct openings, whereby the two cornua uteri communicate with the vagina.
The vagina presents no peculiarity of struc ture, even in the females of those genera in which the penis of the male is furnished with the remarkable armature described above.
The mammary glands in the Rodentia vary much in number, some, as the agouti, having as many as from twelve to fourteen nipples ; whilst in others, such as the Guinea-pig, there are but four.
(T. Rymer Jones.)