Abstract
The effect of strenuous competitive athletics on the heart, that is, the question of true physiological work hypertrophy, is a matter of considerable interest. A study, therefore, of the heart of the greyhound was undertaken. The hearts and body weights of ten of these thoroughbred dogs have been studied and compared with the established normal heart-weight-body-weight ratio of .00798 or 7.98 grams of heart per kilogram of body weight, for ordinary mongrel dogs. 1 The largest heart was found in the oldest and most successful racer, “Victorious Red,” aged three years, with a ratio of 17.3. Five greyhounds that had had their schooling, whose age was about two years and who had raced not more than three times, ranked according to ratio as follows: 16.2, 15.1, 14.5, 13.9, 13.6. Two dogs were full grown, aged eighteen months each, but had not been schooled and had never raced. The one of the better pedigree showed a ration of 13.4, while the other averaged 11.9. Two pups about one-third grown, aged six months each, though leading a caged up, sedentary existence, showed ratios of 11.5 and 11.3, which are above the maximum value of 9.98 found in a series of two hundred ordinary mongrel dogs. 1 The average for the greyhound series is 13.4, which is considerably above that of the stag, 11.5, which has up to this time topped the heart weight-body tables for mammals. Roentgenograms and electrocardiograms of Derby winners in the greyhound races confirmed the anatomical findings. The study suggests that the greyhound, by virtue of generations of strenuous exercise of coursing, or as a result of selection, is endowed with a proportionately large heart at birth and that this heart responds to schooling and training by hypertrophying to an unusual degree.
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