The distinctive event in coitus is ejaculation. This function is dependent on a centre (genito-spinal), which Budge has shown to be situated at the level of the fourth lumbar vertebra. It is a reflex centre. The stimulus that excites it is the ejection of sperma from the vesiculæ seminales into the pars membranacea urethræ, which follows reflexly from stimulation of the glans penis. As soon as the collection of semen, with ever-increasing pleasurable sensation, has reached a sufficient amount to be effectual as a stimulus of the ejaculation-centre, the centre acts. The reflex motor path lies in the fourth and fifth lumbar nerves. The action consists of a convulsive excitation of the bulbo-cavernosus muscle (innervated by the third and fourth sacral nerves), which forces the semen out. In the female as well, at the height of sexual and pleasurable excitement, a reflex movement occurs. It is induced by stimulation of the sensory genital nerves, and consists of a peristaltic movement in the tubes and uterus as far down as the portio vaginalis, which presses out the mucous secretions of the tubes and uterus. Inhibition of the ejaculation centre is possible as a result of cortical influence (want of desire in coitus, emotions in general; influence of the will, in a measure). Under normal conditions, with the completion of the sexual act, libido sexualis and erection disappear, and the psychical and sexual excitement gives place to a comfortable feeling of lassitude. III. GENERAL PATHOLOGY.[28] (NEUROLOGICAL AND PSYCHOLOGICAL.) Abnormality of the sexual functions proves to be especially frequent in civilized races. This fact is explained in part by the frequent abuse of the sexual organs, and in part by the circumstance that such functional anomalies are often the signs of an abnormal constitution of the central nervous system, which is, for the most part, hereditary (“functional signs of degeneration”). Since the generative organs stand in important functional connection with the entire nervous system, and especially with its psychical and somatic functions, it is easy to understand the frequency of general neuroses and psychoses arising in sexual (functional or organic) disturbances. SCHEMA OF THE SEXUAL NEUROSES. } }_a._ Anæsthesia. }1. Sensory. }_b._ Hyperæsthesia. } }_c._ Neuralgia. I. PERIPHERAL.[29] }2. Secretory. }_a._ Aspermia. } }_b._ Polyspermia. }3. Motor. }_a._ Pollutions } } (spasm). } }_b._ Spermatorrhœa } } (paralysis).