974 GENERATIVE APPARATUS. 



tendinous fibres, and partly concealed by the semimembranosus muscles. These 

 erector penis muscles arise from the inferior ischiaic spine, 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 crura into the ischiatic arch. There is 



also a double suspensory ligament proceeding from the ischio-pubic symphysis, 



where it is confounded with the superior attachments of the short adductor of 



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



Fi|^3. cavernosum, a little in front of the point of union of its 



crura. 



Structuee. — This erectile organ is composed, ex- 

 ternally, 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 trabe- 

 culge which partition the interior of the cavity it forms. 

 One of these septa {septum pectiniforme) is directed 

 vertically from the upper to the lower border, and di- 

 TRANsvERSE~%ECTioN OF vldcs thc corpus cavcmosum into two lateral portions 

 THE PENIS, SHOWING THE {corfora cavemoso)^ which would indicate that the crura 



URETHRr WITH THE ^^® "^^ ^^^ °^^^^ ^^ ^^^^^ P^^^^^ ^^ ^^0°' ^^^ ^^^^^^^ 



CORPUS CAVERNOSUM. joiuod to each other. In the Horse, this septum is 

 1, Erectile tissue of the generally Very incomplete, and rarely extends the whole 



corpus caveruosum ; 2, length of the Organ. 



urethral canal ; 4, e^rectile The lamellar prolongations sustain other elastic and 



tissue of the urethra ; 5, contractile bands, which circumscribe the cavities in 

 secttnlf'theTspensory ^^^^ch is lodged the essential portion of the erectile 

 ligament of the penis. tissue. According to Legros, the latter is composed of 

 a network of capillaries interposed between the arterial 

 and venous twigs ; this network shows abrupt or regular dilatations of a diameter 

 varying from •0001 m. to '0015 m. 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 endothelium. In the areolae 

 of the cavernous tissue, particularly towards the base of the organ, the arteries 

 offer a special arrangement ; their walls are very thick, and they soon divide 

 into a bouquet of branches which enter the areolae, where they terminate either 

 by a cul-de-sac, or — which is most frequent — give off small free branches convo- 

 luted in a spiral manner. These are the arterim helkince described by Midler and 

 Rouget. (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 caecal 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 are from the internal pudic 

 and great sympathetic. 



