. SECONDARY SEXUAL CHARACTERS. 43 



would be neutral ; in others it would be deviating more or less in 

 the direction toward the male; in still others toward the female 

 side. On the whole the male would usually deviate to the male 

 and females to the female side. However, differences exist in 

 this respect in different classes and species of animals and also 

 in individuals of the same species. There are, furthermore, dif- 

 ferences in the relative degree of stability of this point of equilib- 

 rium. In insects it is apparently very stable and little or not at 

 all influenced by hormones of gonads; in mammals the equilib- 

 rium is labile and readily influenced by hormones of the gonads. 

 In mammals, the male hormones can be compared to weights 

 added to the male side of the scales and female hormones in- 

 fluence the scales in the opposite direction. It seems probable 

 that in our case we had to deal with an individual with imperfect 

 male gonads which represented a system with a very slight ten- 

 dency towards the male side and with a relatively strong ten- 

 dency toward the female side. In such an individual with ten- 

 dency toward female secondary sexual characters even a strong 

 male hormone is not able to prevent the growth of the mammary 

 gland, and this female tendency is probably in some way con- 

 nected with the suppression of male secondary characters during 

 embryonic development, and perhaps also directly or indirectly 

 with the failure of the testicle to descend to its proper place and 

 develop perfectly. In such a relatively stable system tending 

 toward femaleness in its secondary characters, even a specific 

 male hormone, such as is supplied by the interstitial gland of the 

 testicle, has little chance to become effective. Whether, under 

 certain conditions, the hormone given off by the interstitial 

 gland of the testicle might in addition be able to promote growth 

 of the mammary gland, cannot be decided on the strength of the 

 evidence which we have at present. 



SUMMARY. 



1. It is shown that in a guinea pig with undescended testicle, 

 in which spermatogonia were lacking, and the interstitial gland 

 was hypertrophic, sexual desire was strongly developed. 



2. An attempt is made to analyze the various factors that de- 

 termine the growth of the interstitial gland in the testicle. 



