EEECTILE TISSUES. 337 



is largely supplied, and is analogous to the elevations in the 

 follicles of the skin from the same cause, in what is called 

 goose-flesh. In the vagina, congestion may occur, as in other 

 mucous membranes, but there is no proper erection. 



The vascular arrangement in erectile organs, of which the 

 penis may be taken as the type, is peculiar to them, and not 

 found in any other part of the circulatory system. Taking 

 the penis as an example, the arteries, which have an unusually 

 thick muscular coat, after they have entered the organ, do not 

 simply branch and divide dichotomously, as in most other 

 parts, but send off large numbers of arborescent branches, 

 which immediately become tortuous, and are distributed in 

 the cavernous and spongy bodies in numerous anastomosing 

 vessels, with but a single thin homogeneous coat, like the true 

 capillaries. These vessels are larger, even, than the arterioles 

 which supply them with blood, some having a diameter 

 of from -j^g- to -fa of an inch. 1 The cavernous bodies have an 

 external investment of strong fibrous tissue of considerable 

 elasticity, which sends bands, or trabeculse, into the interior, 

 by which it is divided up into cells. The trabeculse are com- 

 posed of fibrous tissue mixed with a large number of smooth 

 muscular fibres. These cells lodge the blood-vessels, which 

 ramify in the tortuous manner already indicated, and finally 

 terminate in the veins. 2 The anatomy of the corpora spon- 

 giosa is essentially the same ; the only difference being that 

 the fibrous envelope and the trabeculse are more delicate, 

 and the cells are of smaller size. 



Without going fully into the mechanism of erection, 

 which comes more properly under the head of generation, it 

 may be stated in general terms that during sexual excite- 



1 ROBIN, Observations sur la Constitution du Tissu Erectile, Paris, 1865. 



2 J. Muller professed to have discovered a peculiarity in the arteries of erectile 

 tissues consisting in arborescent diverticula from the main vessel, with blind ex- 

 tremities. These he called the helidne arteries. (Manuel de Physiologic. Trad. 

 parJourdan, Paris, 1851, tome i., p. 181.) Rouget in his admirable article (loc. 

 cit.) has gone over the experiments of Muller, and shown conclusively that the 

 so-called helicine arteries do not exist ; and that the appearances described by 

 Muller are due to imperfect filling of the vessels by the injection. 



22 



