TSE MALE GENITAL ORGANS. 865 



arise from the ischial crest, and terminate on the membrane enveloping the 

 crura of the penis, which they cover posteriorly and externally. 



The anterior extremity of the corpus cavernosum forms a blunt point, and 

 is surrounded by the spongy tissue of the glans. 



Mode of attachment of the corpus cavernosum. — The chief attachment is 

 constituted by the insertion of the two crui-a into the ischial arch. There is 

 also a double suspensory ligament proceeding from the ischio-pubic sym- 

 physis, where it is confounded with the superior attachments of the short 

 adductor of the thigh, and passes to the dorsal border of the corpus 

 cavernosum, a little in &ont of the point of union of its crura. 



Struotuee. — This erectile organ is composed, externally, of a white, 

 elastic, fibrous envelope, remarkable for its thickness, especially on the 

 dorsum ; it gives off, from its inner face, a certain number of lamellar 

 trabecule which partition the interior of the cavity it forms. One of these 

 septa (septum pectiniform) is directed vertically from the upper to the lower 

 border, and divides the corpus cavernosum into two lateral portions (corpora 

 cavernosa), which would indicate thut the crura are not one mass at their 

 point of union, but merely joined to each other. In the Horse, this septum 

 is generally very incomplete, and rarely extends the whole length of the 

 organ. 



The lamellar prolongations sustain other elastic and contractile bands, 

 which circumscribe the cavities in which is lodged the essential portion of 

 the erectile tissue. According to Legros, the latter is composed of a 

 network of capillaries interposed between the arterial and venous twigs, and 

 which shows abrupt or regular dilatations of variable diameter. These 

 successively dilated capillaries have very thin walls, which are adherent to 

 the contractile prolongations of the envelope, and are lined by a very 

 delicate pavement epithelium. In the areolse of the cavernous tissue, 

 particularly towards the base of the organ, the arteries offer a special 

 disposition ; their walls are very thick, and they soon divide into a bouquet of 

 branches which enter the areolse, where they tei'minate either by a cul-de- 

 sac, or, which is most frequent, give off small free branches convoluted in a 

 spiral manner. These are the arterice helicince described by Miiller and 

 Eouget. (The walls of the cells are composed of white and yellow fibrous 

 tissue, and unstriped muscular fibres. The cells themselves are in reality 

 venous sinuses. KoUiker found a minute artery to proceed from each of 

 the csecal terminations of the helicine arteries, and terminate, like the other 

 capillaries, in the veins. The dilated vessels have been regarded by some 

 anatomists as only vascular loops. The cells, during the erection of the 

 penis, are distended with blood.) 



The arteries of the corpus cavernosum and dorsales penis pass into the 

 erectile structure, and supply this organ with blood. The collateral veins of 

 these arteries arise near the surface. The nerves come from the internal 

 pudic and great sympathetic. 



6. The Penis. 



The penis is the male organ of copulation, and results from the union of 

 the corpus cavernosum and the spongy portion of the urethra. These parts 

 have already been described ; it now remains to consider the organ in its 



entirety. 



The penis commences at the ischial arch, passes between the thighs 

 and the two dartoid sacs containing the testicles, and is prolonged beneath 

 the belly, where it terminates in a free extremity. 



