138 PHYSIOLOGY CHAP. 



Worthy of consideration also are the bulbo-urethral or Cowper's 

 (/lands, which have a tubulo-alveolar structure similar to that of 

 the prostate. They are two small glands of the size of a pea, 

 but they can be much larger. They are placed at the side of the 

 median line between the posterior part of the urethral bulb, and 

 the membranous urethra (Fig. 28, 1}. Their excretory ducts are 

 3-4 cm. long and open on the inferior border of the bulbar fossa 

 of the urethra with little cleft-like orifices. Cowper's glands are 

 surrounded by smooth muscular fibres, on which are also super- 

 imposed strands of the "bulbo-cavernosus muscle, which, contracting, 

 can compress the gland and squeeze out the contents. The 

 secretory cells are supplied by the nervus pudendus. The secretion 

 of Cowper's glands is a viscous alkaline liquid of the importance 

 of which little is known. Probably their function is similar to 

 that of the little alveolar glands which are scattered throughout 

 the whole course of the urethral mucous membrane. Stilling 

 is of opinion that this secretion serves to secure an alkaline re- 

 action to the urethral mucus, which, after micturition, may be 

 acid, and harmful to the vitality of the spermatozoa. It has 

 been observed that in eunuchs the glands of Cowper do not 

 atrophy ; this would exclude the view that their activity is con- 

 fined to the sexual function. Hugier, however, observed that 

 they increase in size at the time of puberty ; Schmidemiihl found 

 that they diminish in castrated animals, and Stilling described 

 the changes which they undergo after long abstentions, or 

 repeated coitus. It is then clearly demonstrated that they 

 participate in the sexual functions, and empty their contents 

 during copulation. 



IV. The copulatory organ is represented by the virile member 

 (penis), in which are distinguished a root (or fixed perineal 

 portion), and a body, and glans, which constitute the free, pen- 

 dulous, copulatory portion. 



It varies much in volume and dimensions according to the 

 state of flaccidity or erection. In the adult the free part of the 

 flaccid penis has an average length of 10 cm. and a circumference 

 of 9 cm. ; in complete erection it reaches an average length of 

 15 cm. and a circumference of 12 cm. Independently of the 

 state of erection, the dimensions of the penis vary much, from 

 extreme cases of excessive smallness, dependent on arrest of 

 development, to cases of development so great that coitus is 

 difficult or impossible. 



The penis is constituted in great part of erectile tissue dis- 

 posed in three long masses, almost cylindrical, enclosed in fibrous 

 sheaths and united in such a way as to form a three-faced prism 

 with rounded edges, and covered by a common integument. 



These three masses are the two corpora cavernosa of the penis, 

 and the corpus spongiosum or corpus cavernosum of the urethra, 



