SOME POSSIBLE BEARINGS OF GENETICS ON PATHOLOGY 21 



There is a race of fowls known as Campines in which there 

 are two kinds of males, hen- feathered males and cock- feathered 

 males. If the hen-feathered male is castrated, the new feathers 

 that develop are the long feathers of the cock-feathered male, Fig. 

 10. In another race of fowls, Sebright bantams, only the hen- 

 feathered males are known. If these are castrated, the new feath- 

 ers that develop are the long feathers characteristic of all other 

 races of poultry, Fig. 1 1. 



\ 



Fig. ii. To left (a) hen-feathered Sebright cock. To right (b) cas- 

 trated Sebright cock that has developed characteristic cock-feathering. 



If the Sebright male is outcrossed to a hen of another breed 

 in which only cock-feathered males occur, it will be found that 

 all the first generation males are hen- feathered. If these are now 

 bred to their sisters there are produced, in the second generation, 

 three hen-feathered males to one cock-feathered male, showing 

 that the difference between the two races is inherited, Fig. 12. 



Now in this case we can perhaps go further. An examination 

 of sections of the testes has shown that in the hen-feathered Se- 

 bright male there are certain kinds of cells, called luteal cells, while 

 these are absent in the sections of the testes of normal cocks. 

 These same luteal cells are like those present in the stroma of the 

 ovary of all female birds. If we assume that they make an in- 

 ternal secretion that prevents the development of cock-feathering, 



