10 GONADECTOMY IN KELATION TO THE SECONDARY 



while the feathers of his rump have no brown edging, as in both old 

 and young females. 



The exact nature of the juvenile characters must be taken into con- 

 sideration when discussing the results of castration. The mere fact 

 that a closer resemblance exists between the female and the young than 

 between the male and the young can not be taken as an indication that 

 the young are more female than male. The most obvious explanation 

 of the resemblance is that the characters of both are protective and 

 that natural selection has preserved them. 



THE^OPERATION. 



The operation in each sex is very simple, the only difficulty being in 

 the proximity of the great blood-vessels — the iliacs and the inferior vena 

 cava — directly upon whose surfaces lie the organs of reproduction. In 

 both males and females the preliminary steps are identical, except that 

 for best results the male should be opened on each side. The female is 

 opened on the left side only. 



THE ANESTHETIC. 



The anesthetic and method of administering it vary with the age 

 and depend also upon whether the bird is a duck or chicken. Ether is 

 the main dependence for most operations. This is given by inserting 

 the head of the bird, or sometimes the beak only, into a bottle contain- 

 ing the anesthetic on cotton. Ducks have a trick of holding their 

 breath the moment their head is inserted. They will inhale, however, 

 the moment the bottle is withdrawn, so that by making false move- 

 ments they may be induced to inhale the anesthetic. Aid may also 

 be had by massaging the abdomen and chest. After a few inhalations 

 have taken place the duck loses the power of inhibiting the respiration 

 and begins to breathe regularly. With older ducks it is sometimes 

 difficult to give enough ether readily in this way. Chloroform conse- 

 quently is used for the first four or five breaths, just enough to over- 

 come the duck's control of the inhibitory mechanism of respiration. 

 More can not be used, for chloroform with both ducks and fowls is 

 often quickly fatal. Very young birds are so susceptible to the influ- 

 ence of ether that it is difficult to keep them in exactly the right con- 

 dition. By skillful manipulation, however, the bird may be kept in 

 good working shape. With older birds the period during which the 

 ether is given lengthens, while the intervals during which the ether is 

 kept away become continually shorter until, with ducks 3 or 4 months 

 old, it is necessary to give all the ether they will take after the abdom- 

 inal cavity is opened; for as soon as this is done much less ether appears 

 to be absorbed on account of the structure of the respiratory mech- 

 anism. It is usually advisable to have the bird thoroughly under an 

 anesthetic before the opening is made, otherwise it is often impossible 

 completely to narcotize the animal. 



