COMPENSATORY HYPERTROPHY OF THE TESTES. 461 



twenty-four weeks and the fourth between thirty-two and forty 

 weeks of age at the time of operation. 



The operated birds and their controls in each group were 

 hatched at the same time and kept in the laboratory under 

 identical conditions. Comparisons were made only within the 

 groups and in no case between birds of the same age but hatched 

 at different periods. 



The cockerels and their controls were weighed at the time of 

 operation and the measurements of the head furnishings and 

 spurs taken. These observations were repeated every eight 

 weeks and a record kept of the condition of the experimental and 

 control birds during the entire experimental period. The testes 

 were removed through an incision between the last two ribs, the 

 gland rapidly weighed and the volume obtained through displace- 

 ment of normal saline. In the group of baby chicks where the 

 testes were removed at about one week of age, the gonads were 

 not weighed, but the length and w r idth of the gland taken with 

 a pair of fine callipers. The removed testes were fixed in Bouin's 

 fluid at 37 C. and kept in the incubator at that temperature 

 for several hours, varying with the size of the gonad. The 

 usual procedure was followed in washing, etc., and the testes 

 preserved in oil of wintergreen for future histological work. 



The greater number of the chicks operated upon at one week 

 of age was lost together with their controls owing to unfavourable 

 weather conditions. The survivors were kept until they were 

 thirty-two weeks of age and then completely caponized or killed. 



In the three other groups the right gonad was removed from 

 a certain number of cockerels and the left from a similar number. 

 The surviving right or left testis was then retained for eight, 

 sixteen and twenty-four weeks respectively, at the end of each 

 of these periods one cockerel having a right testis, one cockerel 

 having a left testis and two control birds were completely 

 caponized or killed. 



We found in the course of our observations that loss of weight 

 on the part of the cock is reflected in a corresponding diminution 

 of the size of the testes. 



The data obtained are outlined in the tables given below. 

 The age of the bird at the time of the operation, the weight of 



