592 GEOFFREY SMITH. 



This conclusion has been accepted, as proved by Dr. 

 Walker's experiments, by a number of authorities on sex. 



Since this conclusion, that the injection of testis extract 

 into the female calls forth the production of certain secondary 

 sexual characters of the male, is one of considerable theoretical 

 importance, and since it rests at present entirely on the experi- 

 mental evidence furnished by Dr. Walker, it appeared to me 

 desirable to repeat the experiment on a rather larger scale, 

 and to control the experiment with measurements on normal 

 hens. It may be at once stated that the result of this inquiry 

 has convinced me that the comb of the adult hen is usually in 

 a state of fluctuating growth, varying between wide limits, 

 and that this fluctuation is entirely uninfluenced by the injec- 

 tion of extracts of the cock's testis. Out of nine birds injected 

 onl}' one showed fluctuations in growth which fell outside the 

 variability of the control birds, the other eight giving abso- 

 lutely negative results. In the course of the experiments I 

 also tested the influence of the injections upon the fertility of 

 the eggs and upon the properties of the blood-serum of the 

 injected birds. 



The whole of the experiments have been done in the Depart- 

 ment of Pathology, Oxford, under the supervision of Prof. 

 Dreyer, to whom I tender my most hearty thanks for the help 

 be has given me. 



1. Methods Employed. 



As I was desirous of repeating Dr. Walker's experiments 

 in the same manner as he performed them, the extract was 

 made by crushing up the fresh testes of a cock with twice their 

 weight of sterile saline and straining the emulsion through 

 gauze. In this way everything except skin and connective 

 tissue passes into the extract, which forms a fine emulsion. 

 Dr. Walker injected the hens with *o c.c. of such an emulsion 

 every day. I have used various methods, in certain cases 

 injecting the birds with greater amounts, up to as much as 

 10 c.c, at intervals of a few days, in other cases injecting 



