2 i8 NORMAL HISTOLOGY. 



the veins, during erection become enormously distended, with a cor- 

 responding reduction in the thickness of the intervening trabeculae. 



The corpus spongiosum in its structure resembles closely the 

 cavernous bodies, being limited by a fibrous tunic from which spring 

 the trabeculae of the cavernous tissue enclosing the venous spaces. 

 The fibrous envelope is less developed than in the case of the 

 cavernous bodies, while the proportion of elastic fibres is greater, 

 peculiarities resulting in less unyielding rigidity in this part of the 

 penis during erection. The fibrous trabeculae of the spongy body 

 are thinner but more uniform in diameter, and the enclosed spaces 

 possess greater similarity in size, although somewhat smaller than the 

 corresponding channels of the corpora cavernosa ; their long axis 

 generally coincides with that of the penis. The erectile tissue of 

 the corpus spongiosum is continued into the glans, the spaces, how- 

 ever, becoming somewhat reduced and provided with finer trabeculas. 

 Immediately around the urethra a zone of condensed fibrous tissue 

 intermingled with a quantity of unstriped muscle occurs, in addition 

 to which a small amount of muscular tissue frequently exists within 

 the fibrous tunic of the spongy body, as well as within the larger 

 trabeculas. 



The smaller divisions of the arteries of the cavernous bodies, 

 branches of the internal pudic, are supported by the larger bands of 

 fibrous tissue ; from these situations the arteries pass into the capil- 

 lary vessels, which, as a rule, communicate with the blood-spaces of 

 the erectile tissue ; these spaces, in turn, are drained by the venous 

 radicles, which empty into veins escaping at the roots of the penis 

 or into the dorsal vein. Not all the capillaries, however, open into 

 the cavernous spaces, since those destined for the nutrition of the 

 tissues at once terminate in the veins, thus establishing a direct cir- 

 culation, which forms the chief course of the blood during the passive 

 condition of the penis. As a compensative provision for the great 

 expansion of the trabeculas during erection, the arterioles are often 

 so long that they present marked tortuosity, sometimes protruding 

 as twists and loops into the undistended cavernous spaces ; in recog- 

 nition of this peculiarity these vessels have been named the helicine 

 arteries. 



In addition to the usual channel of the blood into the spaces by 

 means of the capillary vessels, a direct communication exists between 

 the arterioles and the larger spaces at the circumference of the cavern- 

 ous bodies (Langer). The arrangement of the vascular supply of 

 the corpus spongiosium and of the glans is identical with that above 

 described, all the blood, however, being conveyed into the spaces 

 through the capillaries. 



The masses of erectile tissue, enclosed within their respective 



