PHYSIOLOGY, CHEMISTRY AND PATHOLOGY 459 



though they were females. The "mother instinct" to protect and nurse 

 the young is also noticeable. On the other hand, young female rats have 

 been converted into such apparently mature males that they react psychi- 

 cally as males and imitate the normal male in a very exact way in the act of 

 copulation. Further, Sand has demonstrated that artificially produced 

 hermaphrodites show a mixed psycho-sexual character, that is, they demon- 

 strate activities peculiar to both sexes. From such observations it appears 

 as though the somatoplasm acts simply as an indicator of sex differentiat- 

 ing stimuli. 



Erection Centers of the Spinal Cord and the Testes. The sexual 

 orgasm is usually accompanied by a high degree of mental excite- 

 ment, although the act of copulation is essentially a reflex action. The 

 nervous centers presiding over this function are located in the lumbar 

 cord (Goltz, Sherrington, Langley, Spina, Budge and Eckhard). The 

 afferent nerves for the ejaculatory reflex are the sensory nerves of the 

 penis, especially those of the glans penis. The lumbar center is also open 

 to stimulation from the higher centers, i. e., cerebral or conscious areas 

 (Pussep). However, erection and ejaculation may be induced when all 

 connections with the brain are removed by transaction of the spinal cord 

 (Onuf, Goltz). 



Early castration results in varying degrees of loss of the power to 

 perform the sexual act. Atrophic changes in the testes of adults also often 

 causes a loss of libido and the power to perform the sexual act. Simpson 

 and Marshall have shown that it is difficult or impossible to induce erection 

 experimentally by stimulation of the nervi erigentes in animals castrated 

 prior to puberty. It is possible that in such animals the musculature of 

 the penis fails to develop sufficiently to admit of erection. On the con- 

 trary, if erection is due mainly to an inhibition of the vasomotor nerves to 

 the penis, as is commonly taught, the inhibition of these nerves must in 

 some way depend upon the proper functioning of the interstitial cells. An 

 overaction on the part of the testicular hormone is said to result in an in- 

 creased libido and power to perform the sexual act (Day). 



Genito-Vesicular Reflex and the Testes. During the ejaculation of 

 semen the capacity of the bladder is increased and its contents pre- 

 vented from discharging because of the muscular closing of the neck of 

 the bladder and relaxation of the bladder walls. According to Ser- 

 ralach and Pares, similar changes occur in the bladder following the in- 

 jection of extracts of testicular substance. Extracts of the prostate 

 also cause contraction of the bladder. According to Du Bois and Boulet 

 the intravenous injection of extracts of the normal prostate causes 

 contraction of the bladder. Extracts of hypertrophied human prostate 

 glands have no such effect in most cases, and when they do the result 

 is because of the presence of normal tissue in the hypertrophied gland. 

 According to this finding the retention of urine in subjects of hyper- 



