HEREDITY OF RACEHORSE STAMINA 45 



movements such as are brought to play in galloping 

 at racing pace. Here we are not concerned with the 

 staying power of an individual muscle, but with 

 that of almost the whole of the striated skeletal 

 group, and the heart included. 



The Severity of the Racecourse Test as a 

 Selective Agent. 



By the racecourse test, it is true, we are not able 

 to measure in foot pounds per second the amount 

 of work done by the muscles of a racehorse before 

 fatigue {i.e., muscle asphyxiation) commences ; but 

 the graduated series of distances over which races are 

 run in Great Britain and Ireland provides a test 

 which, though perhaps not entirely free from error, 

 is, nevertheless, a reliable standard by which an 

 individual horse's racing stamina can be assessed. 



In order to appreciate fully the part played by 

 the racecourse as a selective agent for stamina, it is 

 necessary to draw attention to the rules of the Jockey 

 Club bearing on the distances to be run and the 

 apportionment of stake money for these distances. 

 These rules provide : — 



(1) That no horse or mare of three years old and 

 upward shall run over a less distance than five 

 furlongs. 



(2) There shall not be more than two races per 

 diem of less distance than seven furlongs, 

 only one of which may be of less distance than 

 six furlongs. 



