STUDIES TN THE EXPERIMENTAL ANALYSIS OF SEX. 289 



rnent in the germinal part of the glands^ the interstitial cells, 

 forming islets everywhere between the testicular tubes, were 

 well marked. 



There was no trace of infection by the tubercle bacilli in 

 either testis. 



It is clear from the course of the disease and from the post- 

 mortem examination that the reduction of the comb and 

 wattles and the atrophy of the testes went hand in hand with 

 the acute development of the tuberculosis. We know from 

 numerous experiments that the effect of the removal of the 

 testes in Gallus is to arrest the developmentof the comb and 

 wattles ; otherwise, except for the loss of the crowing and 

 the drooping of the tail, the other secondary sexual characters 

 are not affected. We have seen that as the bird in question 

 became ill, the principal symptom was the reduction in the 

 comb and wattles, and the post-mortem showed that the 

 testis must have been accompanying these organs in a process 

 of atrophy. 



We have, therefore, in this case, an instance of parasitic 

 castration caused by a bacterial infection of a vertebrate host, 

 exactly parallel to the cases of parasitic castration in various 

 Invertebrata caused by such various parasites as Crustacea, 

 Sporozoa, and worms of various kinds. In a great number 

 of these cases the effect of the parasitic castration is to 

 arrest the development or cause the atrophy of the primary 

 and secondary sexual characters without actively calling 

 forth the production of the female sexual characters in 

 the parasitised male. In other cases (as far as we know 

 only in the Crustacea) besides the suppression of the sexual 

 characters both primary and secondary proper to the 

 infected individual, we find the active assumption of female 

 characters by the parasitised male, as described in Parts 2 

 and 3 of these studies. The particular case just described 

 belongs, as far as the evidence goes, to the former of these 

 two categories, i. e. that in which certain of the male sexual 

 characters atrophy without the active assumption of female 

 characters. The principal interest attaching to this case 



