STUDIES IX THE EXPERIMENTAL ANALYSIS OF SEX. 457 
no evidence that the pad has undergone any reduction, either 
in glands or papillae, since September when castration was 
performed. 
No. 16. — Male frog, with moderately rough, swollen and 
pigmented pads, was castrated on October 11th, 1910. No 
obvious change took place in the thumb, and the animal was 
killed on February 19th, 1911, i. e. after a period of four 
months. Sections (fig. 25) of the pad show very much the 
same condition as in No. 15; there is no evidence of the pad 
returning to the smooth reduced condition of the summer frog*. 
The effects of castration, therefore, are to make the thumb 
remain in much the same condition as it was when castration 
was effected, except in the case of the breeding spring-frog, 
when castration is followed by a rapid shedding of the pads. 
We have now to follow the effects which ensue when a 
male frog is castrated and testes are inplanted into it, or the 
animal is injected with testis extract. Some of the animals 
used in this experiment have been previously described under 
the transplantation experiments. 
No. 11.— Male frog, in which testes were severed and left m 
the abdominal cavity on October 4th, 1909. The thumb-pads 
at the time were somewhat pigmented, swollen, and covered 
with small papillas, and while the frog was under observation 
the thumb-pads certainly did not shrink or become smoother 
or paler, and it was thought, though without much certainty, 
that these characters slightly increased. On February 10th, 
1910, two testes from another frog were cut into pieces and 
inserted into the dorsal lymph-sac. On March 30th, 1 910, the 
animal, being in good health and active, was killed, the 
severed and inserted testes were examined by microscopic 
sections, and the thumb-pads were also sectioned. The pieces 
of testis in the dorsal lymph-sac were undergoing disintegra- 
tion and phagocytosis; the severed testes showed living 
spermatogonia, but disappearance of spermatozoa and 
replacement by fibrous tissue. The thumb* (fig. 26) was in 
the condition of a normal autumnal frog, and there was no 
evidence that it had changed during the experiment. 
