594 GEOFFREY SMITH. 



Besides measuring the combs tlie weights of the bii'ds in 

 grammes were taken at regular intervals, and as many observa- 

 tions as possible were made upon the fertility of the eggs by 

 incubation. In certain cases samples of blood were drawn 

 and their action upon suspensions of the testis extract was 

 observed. 



2. The Effect ox the Growth of the Comb. 



In Experiment No. 1 four birds were used, three of 

 them being white Leghorn hens of two years' age and one a 

 buff Orpington of the same age. Two of the Leghorns were 

 injected, namely, Nos. 1 and 2 in the schedule. No. 1 was 

 injected with 35 c.c. extract in the course of twenty-four 

 days. During this period the comb increased 113 per cent., 

 the largest increase observed in any of the experiments. 

 After the cessation of the injections the comb decreased a 

 little and showed subsequent fluctuations of no very decided 

 character, sometimes increasing considerably (see p. 11). 



Bird No. 2 was injected with 102 c.c. in a period of seventy- 

 five days. The comb fluctuated slightly in size, the greatest 

 increase being 23 per cent. 



In the two control birds, which were kept under the same 

 conditions, but were not injected, one showed an increase of 

 24 per cent., the other remained constant. 



The result of this experiment is that in one case the increase 

 of comb in an injected bird was much greater than in the 

 controls ; the other injected bird, which was injected for a 

 longer period, showed about the same increase as one of the 

 control birds, and therefore gave a negative result. In the 

 case of the injected bird which showed a large increase in 

 the comb, there was no constant shrinking of tlie comb after 

 the injections ceased. 



The fluctuations in weight of all the birds did not show any 

 correspondence with the fluctuations in the comb area. 



In Experiment No. 2 six birds were used, all belonging 

 to the same breed, viz. the Indian Jungle fowl, a small breed 



