OP THE GENITAL FUNCTION IN MAN. 335 



more blood would indeed subsist in them during their relaxation, 

 but less than usual would subsist in them during their contraction, 

 and there could be no accumulation, no inflammation. If the neigh- 

 bouring large vessels act more violently than usual, (though their 

 ordinary alternate contraction and relaxation are also hypothetical) 

 they may be conceived to produce an accumulation of blood and 

 a distention of the smaller vessels. 3. If the vessels of any part 

 become dilated and do not contract in proportion, this circum- 

 stance will be sufficient to produce an accumulation, without any 

 necessity for supposing an increased action of the neighbouring 

 larger vessels. This explains inflammation : and in Bichat's 

 Anatomie Descriptive, this explanation is given of erection. The 

 corpora cavernosa which always contain florid blood, spon- 

 taneously dilate, and accumulation ensues. For this purpose it 

 is not necessary that they should be muscular, but Mr. Hunter 

 asserts their muscularity I in a horse he found them muscular to 

 the eye, and they contracted upon being stimulated. 



The heart, however, as in all cases of what is called increased 

 determination of blood, lends its powerful aid by acting with 

 augmented force. 



As to the final cause of erection, the organ, by acquiring 

 increased bulk, firmness, and sensibility, becomes adapted for 

 affording and experiencing to the utmost extent the effects of 

 friction both as exciting pleasure and as stimulating the secreting 

 vessels ; the increased length and narrowness of the urethra ren- 

 der the emission more forcible.* 



(K) If Gall is right in placing the seat of sexual desire in the 

 head, this kind of erection may be explained by supposing the 

 irritation, arising in the cerebellum from the great accumulation 

 of its blood, to produce a correspondent irritation in the organs 



* Mr. Shaw has pointed out a venous network running along the inside of 

 the urethra, but accumulated at what is called the membranous part, connected 

 with the corpus spongiosum, and forming two columns with a groove in the 

 middle. Tins must principally assist in narrowing the canal during erection, 

 and, as the columns unite before the prostate, must also contribute to prevent 

 the semen from moving towards the bladder. Med. Chir. Trans. Vol. x. 



