11 Nov., 1918.] Hereditary Unsoundness in Horses. 



679 



A CONTRIBUTION TO THE STUDY OF HEREDITARY 



UNSOUNDNESS IN HORSES. 



By W. A. N. Robertson, B.V.Sc, Chief Veterinary Officer. 

 (Continued from page 478.) 



FAMILY 7. 



This is the largest family dealt with, there being 871 representatives 

 tabulated. Of this number, 106, or 12.17 per cent, were found unsound. 

 The unsoundness recorded is seen scattered through many generations, 

 there being no line of descent in which it is predominant. The family 

 may, therefore, be considered a sound one, and an analysis will show 

 that most of the unsoundness found can be traced through the dams. 



The following table summarizes the unsoundness in this family. 

 The table departs slightly from that of other families, inasmuch as 

 sub-family 7.3 has been divided into branches 7.311 and 7.312 to 7.36 

 This is done for the reason that through 7.311 we have the largest 

 branch of any family recorded. 



Table Showing Unsoundness in Family 7. 



The descendants of 7.1 show 9.09 per cent, unsoundness. Most 

 of this can be shown to have been transmitted through the blood of the 

 dams, as follows: — 



7.12111 was from a mare by a son of 3.1; very unsound line. 

 7.12102 was from a mare by 2.18. granddam by son oi 3. 

 7.12108 was from a mare probably by a. son of 3. 

 7.12182 was from a mare by 7.492, which, though apparently sound, 

 appears frequently in unsound pedigrees. 

 The dam of 7.121006 cannot be traced. 



