338 CIRCULATION. 



ment, or when erection occurs from any cause, the thick mus- 

 cular walls of the arteries of supply relax, and allow the ar- 

 terial pressure to distend the capacious vessels lodged in the 

 cells of the cavernous and spongy bodies. This produces the 

 characteristic change in the volume and position of the organ. 

 It is evident that erection depends upon the peculiar arrange- 

 ment of the blood-vessels, and is not simply a congestion, 

 such as could occur in any vascular part. During erection, 

 there is not a stasis of blood ; but if it continue for any length 

 of time, the quantity which passes out of the part by the 

 veins must be equal to that which passes in by the arteries. 

 If return by the veins were prevented, gangrene would inev- 

 itably supervene, an occurrence which sometimes takes place 

 when the root of the penis has become constricted, and is not 

 speedily relieved. Erection may be produced in the dead 

 body, by preventing reflux by the veins, and filling the ves- 

 sels contained in the cells of the cavernous and spongy bodies 

 by injection. It has been shown by Miiller that the penis 

 may be made rigid by an injection at a pressure about equal 

 to the pressure of blood in the arteries. 1 



The mechanism of erection of the clitoris, arid other 

 erectile parts, is essentially the 'same as in the penis. It is 

 seen that in this condition, circulation is by no means arrested ; 

 and the tortuous vessels are filled with blood by an enlarge- 

 ment in the caliber of the small arteries of supply. 



Rouget has shown that the body of the uterus possesses an 

 erectile tissue as perfect as that of the penis ; and that after 

 death the organ may be made to change its form and posi- 

 tion by injecting the vessels, when it increases in size about 

 one-half, rising up, and becoming rigid arid erect in the cavity 

 of the pelvis. 2 



This relaxation of the muscular coats of the arteries only 

 exists for a time ; tonic contraction occurs, the supply of 

 blood is diminished, and the organ returns to its ordinary 

 condition. 



1 J. MULLER, op. cit., tome i., p. 182. * ROUGET, op. cit., pp. 338, 339. 



