GENITAL ORGANS 485 



last-mentioned Order they are greatly developed. B. Vesiculce 

 scminales, opening into the ductus ejaculatorius together with 

 the seminal duct : they are usually large, saccular, and tubular 

 structures, and occur in certain Rodents, Insectivores, and Bats, 

 and in Sirenians, Elephants, Ungulates (especially Perissodactyles) 

 and Primates. 



II. Glands arising from the urinogenital canal. A. Prostate glands, 

 fully developed in the male only, enclosed by smooth muscles, and 

 sometimes more or less distinctly subdivided into two or three 

 lobes. The prostate is wanting only in Monotremes, Marsupials, 

 Edentates, and Cetaceans. A median sac, opening into the 

 urinogenital canal, is surrounded by the prostate, and the degree 

 of its development exhibits considerable variation. It is usually 

 described as the vesicula prostatica or uterus masculinus,&i\d in most 

 cases (not, e.g., in Lepus) corresponds to the fused bases of the 

 Miillerian ducts : a more appropriate name would therefore be 

 vagina masculina. B. Urethral glands, present in both sexes in 

 the form of scattered glands, and more definite and localised 

 bulbo-urethral or Cowpers glands, known in the female as the 

 glands of Bartholini. These are phylogenetically the oldest 

 glandular appendages of the urinogenital canal. The scattered 

 glands in some cases are abundant, and in others (e.g. Canidse) 

 are wanting : Cowper's glands are, with few exceptions (e.g. Dog, 

 Bear, aquatic Mammals), of constant occurrence and position : they 

 are surrounded by striped muscle. 



III. Glands of the external genital organs and inguinal region 

 (preputial, inguinal, and anal glands}. These are epidermic 

 structures, and are derivable from sebaceous glands or sweat-glands 

 (cf. p. 33). 



There seems to be no doubt that the secretions of the prostate, 

 ampullary glands, and seminal vesicles have an important relation 

 to the vitality and fertilising power of the spermatozoa, and a high 

 degree of fertility is usually seen in those animals in which these 

 glands are most markedly developed. 1 The secretions of the 

 preputial, inguinal, and anal glands, in addition to protecting the 

 surface of the skin around the urinogenital and anal apertures, is 

 doubtless of secondary sexual importance, owing to the production 

 of odoriferous substances. 



1 In many Mammals (e..(j. Rodents, Insectivores) these glands have also 

 another function. Their coagulated secretion forms a kind of "stopper" for 

 closing the vagina and thus ensuring fertilisation. In certain Bats the mucous 

 membrane lining the neck of the uterus becomes modified directly after copula- 

 tion, and together with the secretion of the accessory genital glands closes 

 the canal and protects the mass of sperms until the following spring, when 

 fertilisation of the ova takes place : it has been shown that the spermatozoa may 

 thus retain their vitality within the uterus for eight months. In some cases the 

 secretion in the vagina originates from the accessory genital glands of the male. 



