8.58 



PHYSIOLOGY. 



All these glands and the seminal vesicles furnish a liquid capable 

 of diluting and liquefying the semi-solid semen as it leaves the vas 

 deferens. The smooth muscles of the vasa deferentia, vesiculae 

 seminales, aided hy the dartos and cremaster muscles, which com- 

 press the testicles, make semen accumulate in the urethra between 

 the congested verumontanum (which prevents its regurgitation into 

 the bladder) and the urethral sphincter. 



The friction of the glans is the cause of the ejaculation. This 

 friction, in a reflex manner, causes the involuntary and spasmodic 

 contraction of the vas deferens and of the seminal vesicles. 



The escape of semen in jets is due to the rhythmic contraction 

 of the bulbo-cavernous and ischio-cavernous muscles, aided by the 

 other muscles of the perineum. Ejaculation is accompanied by a 

 general excitement of the brain. However, Goltz has shown that 

 after a transverse section of the cord in the dog, ejaculation can still 

 ensue. 



Castration. In castrating a bull or a guinea-pig it is found 

 that the thymus is greatly retarded in its stage of atrophy, so that 

 the thymus of an ox exceeds considerably that of a bull. The testes 

 greatly increase in size in guinea-pigs after removal of the thymus. 

 Hence it is probable that the thymus has an internal secretion which 

 controls the growth of the testicles. 



Prostate. The secretory nerve of the prostate gland is the 

 descending branch of the inferior mesenteric ganglion. The vaso- 

 dilator fibers of the prostate are contained in the nervus erigens 

 and its two branches. The vasodilation of erection is accompanied 

 by a vasodilation in the prostate. When atropin is given, irritation 

 of the secretory nerves of the prostate is without effect. Pilocarpin 

 increases the secretion. 



Menstruation. In the adult female during certain age-limits 

 there occurs a discharge from the genitalia once about every twenty- 

 eight days. This periodical discharge consists of blood, dead and 

 disintegrated epithelium from the uterus, and mucus from the glands 

 of the uterus. 



With the discharge of the above-named materials there is usually 

 expelled at the same time one or more ova from their follicles. How- 

 ever, ovulation and menstruation may be, and very often are, inde- 

 pendent of one another. The onset of menstruation is usually her- 

 alded and then accompanied by certain constitutional signs of full- 

 ness and pain in the pelvic region. There is a real congestion of 

 all of the pelvic organs; in particular the uterine mucous membrane 



