242 THE PHYSIOLOGY OF REPRODUCTION 



and Insectivora. The temporal gland of the elephant is also 

 stated to emit a sexual secretion, especially in the male during 

 rut. 



The Copulatoey Organ 



The penis is the intromittent organ of copulation. Besides 

 serving to conduct the urine to the exterior through the 

 channel of the urethra, it has the further function of conveying 

 the semen into the genital passages of the female. This latter 

 function is dependent upon its power of erection under the 

 influence of sexual excitement. 



The erectile tissue of the penis is contained chiefly in three 

 tracts, the two corpora cavernosa, which are situated one on each 

 side and are united in the middle hne, and the smaller corpus 

 spongiosum, which is placed inferiorly and surrounds the urethral 

 passage. The corpora cavernosa are enclosed by an invest- 

 ment, containing plain muscle fibres, numerous weU-developed 

 elastic fibres, as well as bundles of white fibres. Trabeculae 

 pass inwards from the fibrous sheath and cross the cavities 

 of the cavernous bodies, dividing them into interstices which are 

 filled with venous blood, being, in fact, greatly enlarged vessels. 

 The corpus spongiosum is similar in structure, but its fibrous 

 framework is not so well developed. The canal of the urethra 

 is surrounded by plain muscle fibres. Muscular tissue is also 

 present in the external coat of the spongy body, and in the 

 trabeculae. 



At their proximal ends the three corpora are enlarged into 

 bulbs. Those of the cavernous bodies are covered by the 

 ischio-cavernosi muscles (or erectores penis), while the bulb 

 of the spongy body is surrounded by the bulbo-cavernosus 

 muscle (or ejaculator urinse). At its distal end the corpus 

 spongiosum becomes enlarged, forming the glans penis, which 

 is identical in structure with the rest of the body. 



The integument of the penis in the region of the glans be- 

 comes doubled in a loose fold. This is the prepuce or foreskin. 

 Numerous sebaceous glands are present near the free margin 

 of the prepuce. These glands emit an odoriferous secretion which 

 in some animals is especially marked during the season of rut.^ 

 * Conrant, " Uber die Praputialdriisen des Kaninchens und iiber Verander- 

 ungen derselben in der Biunstzeit," Arch. f. Mikr. Anat., vol. Ixii., 1903. 



