STUDIES IN THE EXPERIMENTAL ANALYSIS OF SEX. 459 
was cut off and sectioned (fig. 30). It shows well-developed 
papillae and glands. 
On October 20th, 22nd, 25th, 27tli, and November 1st, 3rd, 
8th and lltli the animal was injected with the substance of 
sixteen fresh testes. 
At no time did the thumb appear to undergo any change. 
The animal died on November 16th, and sections (fig. 31) 
of the uninjured pad showed if anything a slight reduction 
of the papillae owing to peeling of the superficial layers of 
skin. The glands, however, are very well developed — if any- 
thing, better than in the pad before the injections. 
Results op Experiments on Thumb-pad. 
The results of the above experiments show, firstly, that no 
amount of experimental treatment, such as ovariotomy, 
implantation of testes, injection of testis extract, has the 
slightest effect in making the female assume any of the male 
characters of the thumb. Castration in the male, we find, 
causes the thumb to be arrested in its development at the 
stage at which it was when castration was performed ; it does 
not cause any immediate regression to the smooth condition 
even after a period of six months. This, however, only 
applies to autumn and winter frogs; breeding frogs in the 
spring, when castrated, very quickly cast off the external 
pigmented layers of the pads, though colourless papillas of 
considerable size still remain on the pads. 
The results we have obtained from implanting* testes or 
injecting testis extract into castrated frogs have given wholly 
negative results, the thumb remaining in the state in which 
it was at castration. 
We cannot pretend that our experiments on this head are 
complete, but they give us solid ground for criticising the 
conclusions which Nussbauin (1) and, later, Meisenheitner (13) 
have drawn from similar experiments, and our experience 
both with normal and experimental frogs makes us very 
sceptical as to the validity of the results claimed by these 
