78 



TOPOGRAPHICAL ANATOMY OF THE 



region the recognition of two bodies is not difficult, tor here they 

 diverge to form the two crura penis ^ that are attached to the sciatic 

 arch. Elsewhere, however, they are so closely blended, and the septum 

 penis is so imperfect, that a common cavernous body is produced. 

 It is along the urethral surface of this body that a groove is provided 

 for the reception of the urethra and its envelope of erectile tissue. At 

 the base of the glans the corpus cavernosum penis terminates in 

 three processes, of which the two lateral are short and blunt, while 

 the third, nearer the dorsum of the penis, is longer and more pointed. 



The third erectile body is the corpus cavernosum urethrw, 

 associated, as its name indicates, with the urethra for which 

 it forms a complete investment. This, it will be observed later, is not 



Dorsal vessels and nerve. 



Corpus cavernosum penis. 



Urethra 

 M. bulbocavernosus 



Septum penis. 



Ti.nica albuginea. 

 I'rabccula. 



Corpus cavernosum urethrae. 



M. retractor penis. 

 Fig. 35. — Transverse section of the penis. 



limited to that part of the urethra that is situated in the penis, but 

 also surrounds the pelvic part of this tube. In the middle line, between 

 the two crura of the penis, the corpus cavernosum urethrse forms a 

 slight swelling that is to be regarded as the representative of a urethral 

 hulh (bulbus urethrae) such as is present in the dog. 



The glans penis of the horse forms a characteristic rounded 

 expansion at the free end of the organ, most prominent in that part 

 which is in line with the dorsum penis. The projecting free edge of the 

 glans {corona glandis) is succeeded by a collum glandis, by which the 

 glans is superficially marked ofif from the rest of the penis. Dissection, 

 however, shows that a process of the glans tissue (processus dorsalis 

 glandis) is continued along the dorsum of the penis for some eight to 

 ten centimetres behind the collum glandis. The dorsal veins of the 

 penis take their origin in this process. The gians contains a fossa 

 (fossa glandis) of some depth, into which the free terminal part of the 

 urethra projects as a tubular uretJiral process (processus urethralis) 

 that brings the external urethral orifice (orifieium urethrse externum) 

 ^ Crura [L.], pi. of crus, a leg or limb. 



