10 Jtly, 1919.] Hei'editary Unsoundness in Horses. 415 



A CONTRIBUTION TO THE STUDY OF HEREDITARY 

 UNSOUNDNESS IN HORSES. 



Jill ir. .1. .A'. Tiohertson, B.V.Sc, Chief Veterinary Officer. 

 (Continued from page 310.) 



FAMILY 11. 



This is a short family with only 62 representatives, and 16, or 

 25.8 per cent., of them are unsound. The analysis of the family is as 

 follows : — 



T.VDLE .SHOWING PeKCENTAGK UNSOUNDNESS IN FaMILY 11. 



It will be seen, by considering the full table, that the branch through 

 11.1 is a sound one. 11.111 has 15 sound sons and 12 sound and 2 

 unsound grandsons. Only one of the latter, viz., 11.11111 can be 

 traced; his dam was by 2.526. If unsoundness' was dominant in the 

 blood of 11,111, there would not be so many mature horses sound 

 at examination. The unsoundness present in 11,1121 was posaibly 

 inherited from his dam ; she Wias by 9.51, and the granddam carried 

 the blood of 1 in her vein:s. Through 11.2 the reverse picture is 

 presented. 11.2111 was sound as a 7-year-old, yet of 21 sons examined 

 12, or 57 per cent., were defective, many of them as 3-year-olds. At 

 first sight it would appear that 11.2111 must be responsible for the 

 unsoundness, but the furthest analysis that can be made of pedigrees 

 of the dams of his sons shows as follows. First, as regards the sound 

 sons : — 



The dam of 11.21118 Avas apparently by a grandson of 4.4, a sound 

 line. 



The dam of 11.211105 was by a son of 17.1, a sound family. 



The dam of 11.211106 Avas by a grandson of 2, a sound family. 

 Of the unsound sons, the following history can be traced : — 



The dam of 11.21114 aa^^s by 22.2, an unsound line. 



The dam of 11.21115 Avas by 2.217, Avhose sire Avas unsound. 



The dam 11.21116 Avas by 7.47; he Avas not examined; one son Avas, 

 and found unsound." 



The dam of 11.21117 was by 2.219, an unsound horse. 



■471 ajipoars in tli_^ tiblcs .is soiiul ; this is an error: \\? tiad •^idcbonri 



