FACTORS INFLUENCING ACTIVITIES OF THE TESTIS 43 



the seminiferous tubules themselves. In aged males, the interstitial tissue and 

 the seminiferous tubules normally involute and regress with accumulation 

 of large amounts of connective tissue material. In testicular grafts made into 

 the rabbit's ear, Williams ('50) found, when interstitial tissue was present 

 in the grafts, the seminiferous tubules were more nearly normal; when absent, 

 the tubules underwent fibrosis. 



Another function of the LH substance apparently is concerned with release 

 of the sperm from the Sertoli cells. De Robertis, et al. ('46), showed that 

 anterior pituitary hormones possibly cause release of sperm from the Sertoli 

 cells in the toad by the production of vacuoles and apical destruction of 

 the cytoplasm of the Sertoli elements. In testicular grafts Williams ('50) ac- 

 cumulated evidence which suggests that vacuoles and secretion droplets in 

 the Sertoli cells occurred as a result of LH administration. The combined 

 results of these investigators suggest that sperm release from the Sertoli cell 

 is dependent, in some way, upon LH (ICSH) activity. 



A final function is concerned with the physiological maturing of sperm 

 in the reproductive duct, at least in many vertebrate species. The well-being 

 of the epididymis and vas deferens is dependent upon the presence of the 

 male sex hormone (Creep, Fevold, and Hisaw, '36). As the male sex hor- 

 mone results from stimulation of the interstitial cells by the interstitial-cell- 

 stimulating substance, LH (ICSH), the connection between this substance 

 and the physiological maturation of the sperm cell is obvious. 



2. External Environmental Factors and Testis Function 



As we have seen above, the anterior lobe of the hypophysis acts as the 

 main internal environmental factor controlling the testes and, through them, 

 the reproductive ducts. It has been observed also that food, vitamins, and 

 anatomical position of the testis are important influences in regulating tes- 

 ticular function. Furthermore, general physiological conditions such as health 

 or disease have an important bearing upon the gonads (Mills, '19). All of 



Fio. 22. Chart showing the effects of the hypophyseal anterior lobe upon the devel- 

 oping gametes. It also suggests the various factors influencing pituitary secretion of the 

 gonadotrophic hormones. FSH and LH. Observe that the primitive gamete in the cortex 

 of the ovary is subjected to the cortical environment and develops into an oocyte, whereas 

 in the medullary or testicular environment it develops into a spermatocyte. Experiments 

 upon sex reversal have demonstrated that the medullary and cortical portions of the 

 gonad determine the fate of the germ cell. In the male area or medulla, the germ cell 

 differentiates in the male direction, while in the cortex, the differentiation is in the 

 direction of the female gamete or oocyte, regardless of the innate sex-chromosome con- 

 stitution of the primitive germ cell. The fate of the germ cell thus is influenced by four 

 main sets of factors: ( 1 ) Internal and external environmental factors, controlling the 

 secretions of the pituitary body, (2) Environment of the testicular tissue (medulla) and 

 possible humoral substances produced in this tissue, (3) Environment of the ovarian 

 tissue (cortex) and possible humoral substances elaborated there, and (4) Secretions of 

 the anterior lobe of the pituitary body. 



