EJACULATION. RECEPTION OF THE SEMINAL FLUID. 957 



The stagnation of blood in the penis is not complete; otherwise, long-con- 

 tinued erection (priapism, satyriasis) would under pathological conditions give 

 rise to gangrene. 



Blood-stasis in the penis is favored by the fact that the veins of the penis 

 originate in the cavernous bodies, by whose hardening the veins must be com- 

 pressed. Furthermore, there are on the walls of the large veins of the plexus 

 of Santorini trabeculae of unstriated muscle, which in contracting act as columns 

 penetrating into the lumen of the veins and in part hinder the flow of blood. 



The dependence of erection, as a complex motor mechanism, upon the nervous 

 system was demonstrated by the experiments of Hausmann, who observed that 

 erection failed to appear after section of the nerves of the penis in stallions. 

 The erection that occurs in women is less complete and extends to the cav- 

 ern otis bodies of the clitoris and the bulb of the vestibule. During erec- 

 tion the communication between the urethra and the bladder is closed partly by 

 swelling of the caput gallinaginis, a portion of the spongy body of the urethra, 

 and partly through the action of the urethral sphincter, which is connected with 

 the deep transverse perineal muscle. 



EJACULATION. RECEPTION OF THE SEMINAL FLUID. 



In the expulsion of the seminal fluid two distinct factors are to be 

 distinguished, namely: (i) The passage of the seminal fluid from the 

 testicle to the seminal vesicles, and (2) the act of ejaculation itself. 

 The first takes place continuously in consequence of the advance of 

 newly formed seminal fluid through the activity of the ciliated epithe- 

 lium (from the epididymis to the beginning of the vas deferens) and as 

 a result of the gradual peristalsis of the vasa deferentia, which are 

 provided with a well-developed muscular layer. 



For the initiation of ejaculation, however, a strong peristalsis of 

 the vasa deferentia and of the muscular walls of the seminal vessels is 

 necessary. This is brought about through reflex excitation of the 

 ejaculatory center in the spinal cord. As soon as seminal fluid enters 

 the urethra by this means, rhythmic contraction of the bulbocavernosus 

 muscle takes place as a result of distention of the urethra acting as a 

 mechanical irritant, and the seminal fluid is vigorously expelled from the 

 urethra. Both seminal vesicles and both vasa deferentia do not always 

 discharge their contents into the urethra at the same time. With 

 moderate stimulation only one of these may empty itself at a time. 

 Coincidently with the contraction of the bulbocavernosus, the ischiocav- 

 ernosus and the trans versus perinei profundus also contract, but these 

 have no influence upon ejaculation itself. 



Also in the female there occurs under normal conditions, at the height of 

 sexual excitement, a reflex motor process corresponding to ejaculation in the male. 

 This consists of movements analogous to those observed in the male. There 

 occurs, first, a peristaltic movement of the tubes and the uterus from its cornua 

 to the vaginal portion, induced by reflex irritation of t*he genital nerves. Dembo 

 observed in animals general uterine contractions after irritation of the anterior up- 

 per wall of the vagina. As a result of the movement of the tubes and the uterus 

 (which corresponds to the peristalsis of the vasa deferentia in the male) , a certain 

 amount of mucoid fluid normally moistening the uterine wall is expressed into the 

 vagina. This is followed by rhythmic contraction of the sphincter cunni (analo- 

 gous to the bulbocavernosus) , the insignificant ischiocavernosi and the deep trans- 

 versus perinei being at the same time active. As a result of the vigorous contrac- 

 tion of the muscular fibers of the uterus and its muscular round ligaments, the organ 

 becomes erect and descends toward the vagina, its cavity becoming more and 

 more reduced in size, while its mucus contents are expressed. If the uterus 

 later on, after the excitation has ceased, gradually returns to its relaxed state of 

 rest, it aspirates into its cavity the seminal fluid deposited at its orifice (con- 

 ception) . 



