. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 342 COMPARATIVE MORPHOLOGY OF VERTEBRATES. duct is also largely lost, the lower portion sometimes persisting as a small blind tubule imbedded in the prostate gland and known as the uterus masculinus. In the testes between the tubules are small aggregates of cells known as inter- stitial cells, which have recently been shown to be glands with internal secretion. In man their products, which pass into the blood, apparently cause the assumption of the secondary male characters—growth of hair on the face, change of
. Comparative anatomy of vertebrates. Anatomy, Comparative; Vertebrates -- Anatomy. 342 COMPARATIVE MORPHOLOGY OF VERTEBRATES. duct is also largely lost, the lower portion sometimes persisting as a small blind tubule imbedded in the prostate gland and known as the uterus masculinus. In the testes between the tubules are small aggregates of cells known as inter- stitial cells, which have recently been shown to be glands with internal secretion. In man their products, which pass into the blood, apparently cause the assumption of the secondary male characters—growth of hair on the face, change of voice, etc. —at the time of puberty. There would also seem to be some analogous structure in the ovary governing the development of female characteristics and controlling some of the features of menstruation. There are a number of accessory glands connected with the genital ducts, these being usually better developed in the male than in the female. Only the more vd. FiG. 341.—Diagram of male genitalia of beaver, Castor canadensis, after Weber, a, anus; ag, anal gland; b, urinary bladder; gv, gland of vas deferens; oa, opening of anal gland; op, os penis; p, prostate; pp, preputial gland; r, rectum; u, ureter; vd, vas deferens. prominent are mentioned here. The seminal vesicles (present in some rodents, bats, insectivores and in ungulates and primates) are a pair of tubular or saccular glands opening into the vasa deferentia just before their entrance into the urogenital canal. The prostate glands, which occur in all placental mammals with the exceptions of edentates and whales, are connected with the urogenital canal. Farther along the canal are Cowper's glands which occur in almost all mammals as scattered bodies or aggregated into larger masses, and surrounded by smooth muscle. Concerning the functions of these glands considerable uncertainty exists. From the fact that removal of the prostate and the seminal vesicle in rats prevented fertilization, and the further fact
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