334 GENEEATION. 



live functions, as we have traced it in the female. It is evi- 

 dent that this is a subject of great delicacy, and one that is 

 with difficulty brought to the requirements of rigid scientific 

 inquiry ; still it can hardly be avoided in a full account of 

 the physiology of generation, and is a question often pre- 

 sented to the practical physician. 



Although we have not yet considered fully the mechan- 

 ism of erection, but little remains to be said on this subject 

 after our discussion, in another volume, of the general struct- 

 ure of erectile tissues. 1 The cavernous and spongy bodies of 

 the penis are usually taken as the type of erectile organs. In 

 these parts, the arteries are large, contorted, provided with 

 unusually thick muscular coats, and connected with the 

 veins by vessels considerably larger than the true capillaries. 

 They are supported by a strong fibrous net-work of trabec- 

 ulse which contains non-striated muscular fibres ; so that, 

 when the blood-vessels are completely filled, the organ be- 

 comes enlarged and hardened, and can penetrate the vagina. 

 The researches of Eckhard on the nerves of erection show 

 conclusively that the vessels of erectile tissues are distended 

 by an enlargement of the arterioles of supply, and that there 

 is not simply a stasis of blood produced by constriction of the 

 veins, except, perhaps, for a short time, during the period of 

 most intense venereal excitement. In experiments upon dogs, 

 Eckhard discovered a nerve derived from the sacral plexus, 

 stimulation of which produced an increase in the flow of 

 blood through the penis, attended with all the phenomena of 

 erection. This nerve arises by two roots at the sacral plexus, 

 from the first to the third sacral nerves. In the experi- 

 ments referred to, by a comparison of the quantity of venous 

 blood coming from the penis before and during the stimu- 

 lation of the nerve, Eckhard found a great increase during 

 erection. 2 It is probable that, in addition to the arterial 



1 See vol. i., Circulation, p. 337. 



2 ECKHARD, Experimentalphysiologie des Nervensy stems, Giessen, 1866, S. 287. 

 Eobin ( Observations sur la constitution du tissue erectile, lues d la Societe de 



