"If the foregoing statements are true, it is easy to see why the pleasure of the man is much increased when the orgasm occurs at the same time in his partner and himself, for the contractions of the vagina upon the penis would increase the stimulation of all the nerve endings in that organ for which a mechanical stimulus is adequate, and the prominence of the corpus spongiosum and corona would ensure them the greatest stimulation. It seems not improbable that the specific sensation of orgasm rises from the stimulation of the peculiar form of nerve end-bulbs which Krause found in the corpus spongiosum and in the glans. "The characteristic massiveness of the experience is probably due largely to the great number of sensations of strain and pressure caused by the powerful reflex contraction of so many of the voluntary muscles. "Of course, the foregoing analysis is purely tentative, and I offer it only on the chance that it may suggest some line of inquiry which may lead to results of value to the student of sexual psychology." In man the whole process of detumescence, when it has once really begun, only occupies a few moments. It is so likewise in many animals; in the genera Bos, Ovis, etc., it is very short, almost instantaneous, and rather short also in the Equidæ (in a vigorous stallion, according to Colin, ten to twelve seconds). As Disselhorst has pointed out, this is dependent on the fact that these animals, like man, possess a vas deferens which broadens into an ampulla serving as a receptacle which holds the semen ready for instant emission when required. On the other hand, in the dog, cat, boar, and the Canidæ, Felidæ, and Suidæ generally, there is no receptacle of this kind, and coitus is slow, since a longer time is required for the peristaltic action of the vas to bring the semen to the urogenital sinus. (R. Disselhorst, _Die Accessorischen Geschlechtsdrusen der Wirbelthiere_, 1897, p. 212.) In man there can be little doubt that detumescence is more rapidly accomplished in the European than in the East, in India, among the yellow races, or in Polynesia. This is probably in part due to a deliberate attempt to prolong the act in the East, and in part to a greater nervous erethism among Westerns.