REPRODUCTIVE ORGANS IN THE MALE. 293 



fibrous septum between the two corpora cavernosa 

 which becomes thin anteriorly and incompletely 

 separates the two bodies. There is an external 

 fibrous investment, very strong and elastic. This 

 is composed mostly of longitudinal bundles of white 

 fibers with interlacing elastic fibers. These fibers 

 are intimately associated with the median septum 

 and also with connective-tissue trabeculae that 

 ramify through the substance of the cavernous 

 bodies. The substance of the latter is called erectile 

 tissue and is of a spongy nature. The trabeculae 

 anastomose and interlace freely to form a multitude 

 of interstices or cavernous spaces. These are filled 

 with venous blood, and are really a complex system 

 of veins lined by a layer of flattened epithelium as 

 in other veins. In the anterior portion of the penis 

 the venous labyrinth of one corpus cavernosum 

 intercommunicates with that of the other through 

 the incomplete septum. In the erectile condition 

 the corpora cavernosa are distended with blood 

 which is carried away by two sets of veins, the one 

 set joining the prostatic plexus and the pudendal 

 veins, and the other draining into the dorsal vein 

 of the penis. The arterial blood is supplied mainly 

 by branches of the pudic arteries, but the dorsal 

 artery of the penis sends a few branches through the 

 fibrous sheath, particularly in the forepart of the 

 organ. The arteries ramify in the trabeculae and 

 terminate in minute capillary branches that open 

 into intertrabecular spaces. Some of the smaller 

 arteries project into the spaces, forming peculiarly 

 twisted or looped vessels called helicine arteries. 



