SEXUAL HORMONES AND MORPHOGENESIS 467 



the facts. Anyway we must never forget that ''furtherance" 

 and "inhibition" may be the result of very varied changes in 

 the cellular metabolism; further, it must be taken into consider- 

 ation that the different organs or systems upon which the sex 

 hormones act, such as the skeleton, the fat, the condition of 

 hairiness, and so on, are not uniform, and every part of an 

 organ or of a system may have its special relations to the sex 

 gland which are different from those of the others ; it suffices to 

 recall how varied are the reactions of the individual parts of 

 the skeleton to the sex hormones. This is why it is impossible 

 to draw really hard and fast lines between "furtherance" 

 and "inhibition" and lack of influence, as demanded by the 

 scheme which must be regarded as no more than a working 

 •classification. 



It is quite probable, as indicated in the scheme, that some 

 characters furthered by male hormones are inhibited by female 

 hormones and vice versa. This seems to be true especially for 

 the ductus Mxilleri and ductus Wolffii, and possibly also for the 

 corpora cavernosa of the penis and of the clitoris, for the body 

 weight and for the mammary gland ; we have as yet no detailed 

 knowledge on these matters. There is, however, in this instance 

 an evident antagonism between the male and female sex hor- 

 mones. According to Steinach the development of heterologous 

 sex characters is inhibited by the hormones of a given sex. This 

 contention of Steinach is not, indeed, of general validity, as sex 

 differences (or sex characters) may be the result of very different 

 physiological conditions. For instance, the growth of the long 

 bones is inhibited both by male and female hormones, and the 

 sex specific effect which the hormones have on the growth of 

 the long bones is due clearly to the fact that the female hor- 

 mones inhibit growth in a more marked manner, or begin their 

 inhibitory action sooner. In opposition to the assumption 

 that there is an antagonism between male and female sex 

 hormones Moore (1921, p. 168) has objected that "hormone 

 action is not characterized by an inhibition, but by a stimu- 

 lation." This objection is not entirely correct, as Lillie also 

 recognises (1923, p. 71). 



The existence of furtherance and inhibition as well as 

 antagonism of sex hormones appears to exist also in birds. 

 Thus inhibition of spurs by female hormones obviously occurs. 

 The influence of the female hormones on the plumage is a more 



