In accordance with the supreme importance of the part they play, and the intimately psychic nature of that part, the sexual organs, both internal and external, are very richly supplied with nerves. While the internal organs are very abundantly furnished with sympathetic nerves and ganglia, the external organs show the highest possible degree of specialization of the various peripheral nervous devices which the organism has developed for receiving, accumulating, and transmitting stimuli to the brain.[77] "The number of conducting cords which attach the genitals to the nervous centers is simply enormous," writes Bryan Robinson; "the pudic nerve is composed of nearly all the third sacral and branches from the second and fourth sacral. As one examines this nerve he is forced to the conclusion that it is an enormous supply for a small organ. The periphery of the pudic nerve spreads itself like a fan over the genitals." The lesser sciatic nerve supplies only one muscle--the gluteus maximus--and then sends the large pudendal branch to the side of the penis, and hence the friction of coitus induces active contraction of the gluteus maximus, "the main muscle of coition." The large pudic and the pudendal constitute the main supply of the external genitals. In women the pudic nerve is equally large, but the pudendal much smaller, possibly, Bryan Robinson suggests, because women take a less active part in coitus. The nerve supply of the clitoris, however, is three or four times as large as that of the penis in proportion to size. (F.B. Robinson, "The Intimate Nervous Connection of the Genito-Urinary Organs With the Cerebro-Spinal and Sympathetic Systems," _New York Medical Journal_, March 11, 1893; id., _The Abdominal Brain_, 1899.)