Chapter IV 



ARRESTS AND ABERRATIONS IN 

 GENITAL DEVELOPMENT 



A. Asexual or Bisexual Aberrations 



1. Neuters, Freemartins 



So far as known, cattle lead in the production of asexual, 

 or neuter individuals. This may be only apparent, since in 

 cattle, more than in any other animal, the value of the fe- 

 male of breeding age rests almost wholly upon its reproduc- 

 tive powers, and any failure to breed attracts definite atten- 

 tion. It may be that sheep and goats are as frequently neu- 

 ter but that the condition is overlooked. In cattle the neuter 

 is ordinarily one of a pair of twins, of which the other is a 

 male and commonly fertile. The condition, so far as I 

 know, has not been observed when the other twin is a female. 

 Numerous theories have been advanced in an effort to ex- 

 plain the origin of freemartins, or neuters, but the cause of 

 the phenomenon has not been made clear. While ordinarily 

 the neuter is twin to a male, I am unable to verify the gen- 

 eral belief that this is universal. It has been my privilege 

 to examine clinically several neuters which had been regu- 

 larly registered in official herd books and sold as heifers. 

 The rules of breeders' associations forbid the registration 

 of an apparent female which is twin to a bull until the ani- 

 mal has conceived. In some instances where the animal has 

 not been sold, but has been bred by the party for whom the 

 examination was made, I have had personal assurances that 

 it was a single. Some of these cases may be due to fraud 

 upon the part of the breeder. Other animals may be truly 

 singles in so far as birth is concerned, but the conception 

 may have been twin and one embryo may have perished and 

 disappeared. I am inclined to believe that neuters rarely 

 come from a single conception. Accordingly, when examin- 

 ing a neuter which has been registered and sold as a breeder, 



