THE HORMONE THEORY 1G3 



Geoffrey Smith, one of the many promising young 

 scientific investigators whose careers were cut short 

 in the War, maintained views concerning somatic 

 sex-characters different from that which explains 

 their development as due to a hormone from the 

 testis or ovary. Nussbaum in 1905 ^ had recorded 

 experiments on Rana fusca (which is identical with 

 the British species commonly called R. temporaria) 

 which appeared to prove that in the male frog after 

 castration the annual development of the thumb-pad 

 and the muscles of the fore-leg does not take place, 

 and if these organs have begun to enlarge before 

 castration they atrophy again. When pieces of testis 

 were introduced into the dorsal lymph-sac of a cas- 

 trated frog the thumb -pads and muscles developed 

 as in a normal frog. Geoffrey Smith and Edgar 

 Schuster ^ investigated the subject again with results 

 contrary to those of Nussbaum. 



Smith and Schuster begin by describing the normal 

 cycle of changes in the testes on the one hand and 

 the thumb-pad on the other. After the discharge 

 of the spermatozoa in March or April the testes are 

 at their smallest size. From this time onwards till 

 August they steadily increase in size, attaining their 

 maximum at the beginning of September. From 

 then till the breeding season no increase in size or 

 alteration of cellular structure occurs, the testes 

 apparently remaining in a state of complete inactivity 

 during this period. With regard to internal de- 

 velopment, after the discharge of spermatozoa in 

 the breeding season the spermatogonia divide and 



1 'ErgebnisRC cler Anat. unci Entwicklungsgcsch./ Bd. xv. ; PJlugcrs 

 Archiv, Bd. cxxvi., 1909. 



2 Quart. Journ. Mic. Sci., Ivii., 1911-12. 



