Mammalia: Visceral Systems 665 



rabbits. The substance which causes coagulation of the seminal fluid 

 in the vagina of rodents is produced in the prostate. Vesicular glands 

 are lacking in carnivores. In dogs the bulbourethral also are absent, 

 but they are present in the cat. Sloths have neither vesicular nor 

 prostate; the armadillo has no vesicular and a somewhat doubtful 

 prostate; both of these "edentates" have bulbourethral. Vesicular 

 glands are present in sirenians but not in cetaceans — one of many 

 differences indicating that these two types of aquatic mammal are not 

 closely related. In man there are small vesicular and bulbourethral 

 glands and a massive prostate (Fig. 492) which completely surrounds 

 the urethra. Characteristic roundish lamellated concretions of colloid 

 substance are formed in the alveoli of the gland (Fig. 501). In later life 

 the glandular tissue tends to increase and the concretions increase in 

 size and number, with some deposition of calcareous material. The 

 resulting enlargement of the prostate causes it to exert pressure on the 

 urinary passage, tending to occlude it. 



Arising from the inner layer of the fold of skin forming the prepu- 

 tial sac are preputial glands, whose secretion resembles that of the 

 sebaceous glands which ordinarily occur at the roots of hairs, but it 

 may be odorous. In some mammals, especially rodents (e.g., the beaver: 

 Fig. 500), these glands attain great size. The musk-glands of the male 

 musk deer of Asia are highly specialized preputial glands. The dried 

 secretion is the "musk" of commerce, used in making some perfumes. 



The skin surrounding the anus and in the groin and sometimes in 

 more anterior parts of the body produces, in many mammals, glands 

 which secrete odorous substances. These scent-glands are usually 

 present in both sexes, but may be better developed in one sex, usually 

 the male, than in the other. Such are the inguinal glands of some 

 antelopes and the ano-preputial "castor bags" of beavers (Fig. 500). 

 "Castoreum," derived from the beaver's secretion, is used as a 

 medicament and source of perfume. Of similar nature are the anal 

 scent-glands of many rodents and carnivores (e.g., the civet cats — 

 Viverridae — of Asia and Africa; "civet" is another source of dainty 

 perfume!). It is likely that in most cases (e.g., dogs) the odorous secre- 

 tions of these glands have sexual significance. 



