390 INTERNAL SECRETIONS 



by the opening of the membranes, and he thinks that it would 

 be possible to operate on foetuses without causing death and 

 artificial abortion. The experiments of Minoura on hens' eggs, 

 referred to in Chapter VI., are the first really successful steps 

 in solving these special problems in this kind of way. 



Since Matsuyama (1921) and Goto (1922) have shown that 

 female sex organs such as the uterus undergo profound degene- 

 rative changes w^hen parabiotically united with a castrated 

 male, the question arises whether a similar mechanism might 

 not be at work in the case of the freemartin (Romeis, 1922). 

 The question deserves experimental consideration. 



Doncaster has studied the question whether the sterile male 

 tortoiseshell cat may also be considered, like the freemartin, 

 as a transformed female, as in general there are only tortoiseshell 

 females from crossings of yellow and black cats. Doncaster 

 and B amber (1922) have examined the blood vessels of 70 cats 

 with 253 embryos; no anastomosis between the chorionic 

 vessels of the individual embryos was found. 



3. Birds. 

 (a) Different forms of inter sexuality. 



"Changes of sex" in extrauterine life have been described 

 also in birds. The so-called cock-feathering of old hens has 

 long been well known. Cock-feathering or virihty has been 

 observed, according to Gurney (quoted from Pezard, 1918), in 

 26 different species of birds. The cock-feathering is evidently in 

 most of the cases due simply to the ovary becoming inactive or 

 insufficient; it is often a climacteric change, or a change due 

 to some other cause inhibiting the hormonic activity of the 

 ovary. The bird assumes the characters of the neutral form, 

 since the latter resembles in many respects the male type, the 

 cock-feathering being erroneously taken for an example of an 

 intersexual condition, though no intersexuality is really 

 present. The condition is best illustrated by an observation 

 made by Pezard on the pheasant. He (1922 a) has described 

 a female pheasant which, at an age of 13 years, assumed the 

 male plumage ; spurs did not develop, and there was no male 

 behaviour. The iris kept its chestnut colour, which is charac- 

 teristic of the female (the iris is light yellow in the male). A 

 year later the bird moulted and again assumed a male 



