… thoroughbreds put out bigger efforts these days than their muscles, ligaments, suspension systems and bones can easily sustain. Their physical structure is tested to the utmost to maintain the speed they can now achieve with modern training methods.

From the Thoroughbred Record (HotC, p. 163), 6/3/1911:

Somebody once asked a famous Kentucky turfman what was the chief requisite in the makeup of a great racehorse, and the answer was “speed.”

“And what was after that?” was the next question.

“More speed,” was the reply.