458 
GEOFFREY SMITH AXD EDGAR SCHUSTER. 
No. 17. — Male frog, testes removed October 2nd, 1909. 
At this time the thumb-pads were rather small, slightly 
pigmented and rough, but not in so marked a degree as in 
No. 11. 
On February 10th, 1910, two testes were cut up and 
inserted into dorsal lymph-sac. On March 3rd, 6th, 10th, 
14th and 18th the animal was injected with testis extract, 
receiving in this time the substance of twenty-three testes. 
The animal was killed on March 24th, 1910, being at the 
time in good health, and the thumb sectioned. The sections 
(fig. 27) show a condition of the thumb similar to that of a 
not very advanced autumn frog, and there is no evidence that 
the pad has undergone any increase in roughness, gland 
formation, or pigmentation since October, when it was 
castrated. Everything is consistent with the view that it has 
simply remained in the same condition without decreasing or 
increasing. The following two experiments were designed to 
test more accurately if injection of testis extract had any 
effect on the thumb. Unfortunately the animals died soon 
after the experiment was complete, so that some objection 
may be raised on the ground that the animals were not in 
good health. 
No. 18. — Male frog, completely castrated on October 11th, 
1910. 
On October 20th, 1910, a piece of one of the thumb-pads 
was cut off and sectioned (fig. 28). It shows well-developed 
papillae and glands. The frog was then injected on October 
20th, 22nd, 25th, 27th, November 1st and 3rd with the 
substance of twelve fresh testes. 
The pads during the injection showed no visible change. 
On November 6th the animal died, and sections of the 
uninjured pad (fig. 29) showed no increase in papillae, but an 
actual decrease in the size of the glands, probably owing to 
the ill-health of the animal. 
No. 19. — Male frog, completely castrated on October lltli, 
1910. 
On October 20th, 1910, a piece of one of the thumb-pads 
