iv THE GENERATIVE SYSTEM OF THE MALE 141 



concavity the pointed extremities of the corpora cavernosa of 

 the penis and the corpus spongiosum of the urethra. From the 

 fibro-elastic sheath of the urethra emanate and radiate in every 

 direction delicate laminae of connective tissue ; these pass through 

 the corpus spongiosum of the glans, which has the character of 

 a venous maze, rete mirabile, rather than of true cavernous tissue. 

 The veins which form it are wide, repeatedly anastomose, and 

 are provided with a thick tunic of muscular fibres disposed 

 circularly and in part longitudinally (Fig. 34). 



The passage of the blood from the arteries into the system of 

 cavernous spaces of the erectile tissue of the penis takes place in 

 part through the capillary network, in part directly, as by the 



arteriae helicinae. These have a spiral course which facilitates 

 their lengthening during erection. They have well -developed 

 circular muscles, and often possess longitudinal muscular fibres 

 also. 



From the physiological point of view it is noteworthy that in 

 many small arteries of the penis, especially in the helicine arteries, 

 the intima appears to be folded ; this renders it capable of great 

 dilatation during erection, and limits the area during flaccidity 

 (Ercolani, 1869). But still more interesting is the fact observed 

 by Ebner (1900) that these arteries present here and there a 

 peculiar thickening of the intima, in the form of a little cushion 

 projecting into the interior of the vessel ; it is traversed by elastic 

 fibres continued from the membrana elastica interna, and by 

 longitudinal muscular fibres (Fig. 35). These little cushions have 

 apparently the function of a valvular apparatus, which occludes, 



