40 THE TESTIS AND ITS RELATION TO REPRODUCTION 



sponsible. The latter alternative was suggested by the work of Aschheim and 

 Zondek ('27) and Zondek ('30) who concluded that two separate substances 

 appeared to be concerned with the control of ovarian changes. 



Nevertheless, for a time the concept of only one gonad-controlling (gona- 

 dotrophic) hormone was produced by the pituitary, continued to gain atten- 

 tion, and some workers suggested that the two ovarian effects of follicular 

 growth and luteinization of the follicle were due to the length of time of 

 administration of one hormone and not to two separate substances. How- 

 ever, this position soon was made untenable by research upon the gonado- 

 trophic substances derived from the pituitary gland. Studies along this line 

 by Fevold, Hisaw, and Leonard ('31) and Fevold and Hisaw ('34) reported 

 the fractionation, from pituitary gland sources, of two gonadotrophic sub- 

 stances, a follicle-stimulating factor or FSH and a luteinization factor or LH. 

 This work has been extensively confirmed. It should be observed in passing 

 that the male pituitary gland contains large amounts of FSH, although, as 

 mentioned below, the function of the testis and the male reproductive system 

 relies to a great extent upon the luteinizing factor. Some investigators refer 

 to the LH factor as the interstitial-cell-stimulating hormone, ICSH. (See Evans, 

 '47; and also Evans and Simpson in Pincus and Thimann, '50.) 



The action of these two hormones upon testicular tissue, according to 

 present information, is somewhat as follows: If pure follicle-stimulating hor- 

 mone, FSH, which produces only FSH effects in the female, is injected in 

 low doses into hypophysectomized male rats, the seminiferous tubules are 

 stimulated and spermatogenesis occurs. Under these conditions, the interstitial 

 tissue remains unstimulated and the accessories continue in an atrophic state. 

 It has further been demonstrated that slight amounts of the luteinizing gona- 

 dotrophic hormone, LH (ICSH), added to the above injections of FSH, 

 effects a much better stimulation of the spermatogonial tissue, and the inter- 

 stitial tissue also develops well. 



On the other hand, when pure LH (ICSH) is given alone in small doses, 

 spermatogenesis is stimulated with slight or no effect upon the male accessory 

 structures. However, when larger doses of the LH (ICSH) factor alone are 

 injected, the interstitial tissue is greatly stimulated, and the testicular weight 

 increases much more than when FSH alone is given. Furthermore, the acces- 

 sory reproductive structures are stimulated and become well developed, sug- 

 gesting the elaboration of the male sex hormone. In agreement with these 

 results, the administration alone of testosterone, the male sex hormone, in- 

 creases the weight and development of the accessory structures in hypophy- 

 sectomized animals and it also maintains spermatogenesis. It appears, there- 

 fore, that the effects of the LH substance upon the seminiferous tubules and 

 the accessory organs occur by means of its ability to arouse the formation of 

 the male sex hormone. 



