PHYSIOLOGICAL PROPERTIES OF GONADS 387 



dence for this, however, cannot be suppUed by a random compar- 

 ison of one animal with another. There is no indication that the 

 mammary glands are inhibited by a testicle growth, for if the 

 ovary be removed they remain in a rudimentary condition as in 

 the normal male or spayed female. Also in the rat, there is not 

 only an entire lack of evidence of an antagonism, but there is 

 positive evidence to the contrary. Ovaries and testes grow in 

 the same animal in a functional condition: the testicle does not 

 inhibit the growth of an ovarian graft, neither does an ovary pre- 

 vent the growth of a testicular graft. The ovarian graft does 

 not inhibit the growth of the sperm sacs, the penis, the func- 

 tional condition of the testicle, or the psychical nature of the 

 animal. 



The positive modifying effects of the gonads in cases of trans- 

 plantation to an animal of the opposite sex are: 1) in the rat 

 there is some evidence that the psychical nature of the animal 

 undergoes some change toward the sex represented by the gonads, 

 though this is difficult of intelligent interpretation; the presence 

 of the ovary, shown in cases of spaying females, causes a sUght 

 relative reduction in weight, and, 2) in the guinea-pig an ovary 

 grafted in the male can cause a hypertrophy of the mammary 

 gland, and possibly influence the psychical nature of the animal, 

 though my own experiments give no indication of this : a testicle 

 graft in a female can cause the development of the male psychical 

 tendencies, and also may influence the growth of the clitoris until 

 the external genitals appear more like the male condition than the 

 female. In reference to these positive characteristics the writer 

 is in agreement with Steinach, but upon the basis of observations 

 on more than a hundred operated animals the writer can only 

 conclude that there is not only lack of evidence of an antago- 

 nism existing between secretions of the sex glands, but there is 

 considerable evidence to the contrary; and not only evidence, 

 but positive proof, inasmuch as the two opposite sex glands have 

 remained functional in the same animal for a period of from seven 

 to nine months. 



