INTERNAL SECRETIONS 



95 



however, the external changes in mammals are less marked 

 after ovariotomy than after castration of the male, since in this 

 class the female is much nearer the neutral type than the male 

 is, the secondary characters being for the most part positive in 

 the male sex and negative in the female. 



In birds, on the other hand, the male is closest to the neutral 

 type, and consequently removal of the ovary (for there is generally 



Fig. 61. — Ovariotomised brown Leghorn hen. (From Goodale.) The 

 bird shows male feathering and spurs, but the comb and other 

 erectile structures are not hypertrophied. 



only one) leads to an assumption of apparently male plumage, 

 but the more strictly male characteristics are not acquired. 

 Thus ovariotomy in the fowl is follow^ed by the growth of the 

 spurs and the assumption of much of the male feathering (the 

 bird looking at first sight much like a cock), but the comb, hackles, 

 and other erectile structures about the head remain unaffected 

 (Goodale, Pezard, etc.). Similarly the castrated duck, to a great 

 extent, acquires the external characters of the drake (Goodale). 

 The castrated female ostrich also assumes the typical tail feather- 

 ing of the male, and since this is an economic advantage with 



