INHIBITORY NERVES TO THE VASCULAR SYSTEM 95 



Eckhard, the discoverer of the nervi erigentes, has shown that 

 erection is due to a relaxation of the muscular coats of the arterial 

 blood vessels supplying the corpora cavernosa and spongiosa, in 

 consequence of which the blood spurts out of the cut surface of 

 the corpora cavernosa almost as forcibly as out of a cut small 

 artery ; the flow throughrthe dorsal vein of the penis is enormously 

 increased, and the colour of the blood in it becomes arterial rather 

 than venous. Here, then, there appears to be a vascular dilata- 

 tion caused by nervous stimulation for a specific purpose, apart 

 entirely from all connexion with any glandular or muscular 

 metabolism. The nerve in question, the pelvic nerve, which causes 

 this effect, belongs to the sacral outflow, and the only glandular 

 secretion which is known to occur, when this nerve is stimulated, 

 is that of the prostate gland. Barrington has, however, shown 

 that this is not a true secretion, but is due to pressing out of a 

 secretion owing to the contraction of some of the muscles sur- 

 rounding the prostate gland. He has pointed out that a squeez- 

 ing of the gland takes place both when the pelvic nerve and the 

 hypogastric nerve are stimulated, from which he concludes that 

 the muscle fibres round the gland are of two kinds, partly be- 

 longing, to use my nomenclature, to the cloacal muscles, partly 

 to the uro-dermal group. He finds no evidence of true secretory 

 fibres in the pelvic nerve, but marked evidence of their existence 

 in the hypogastric nerve ; the evidence is also clear that the 

 hypogastric supplies Cowper's glands and Bartolini's glands with 

 secretory fibres. If then the metabolic products of the activity 

 of any of these glands were concerned in the causation of erec- 

 tion, the nervus erigens ought to be found in the hypogastric not 

 in the pelvic nerve. 



At present I conclude that the phenomenon of erection can 

 be best explained by the action of inhibitory nerves to the mus- 

 cular walls of the arteries of the penis. 



In the case of the bucco-facial dilatation, of the nervi erigentes, 

 of the kidneys and of the muscles, the nerves which produce 

 the vascular dilatation have been shown to leave the cord by the 

 anterior roots, and it has been presumed also that the nerves in 

 the sciatic, which on slow rhythmical stimulation cause a redden- 

 ing and rise of temperature in the foot, are also anterior root 

 nerves. Here, however, there arises a new and most unexpected 

 factor in this question of the existence of vaso-dilator nerves, for 



