There is no book - there can be no book - that will infallibly point the way to successful bloodstock breeding. Yet, as Senator Tesio observed, the sport of horse racing has produced, in the General Stud Book, a genetic record extending now over more than two centuries and a score of generations, that contains an ordered store of facts such as no scientific body possesses about the hereditary qualities of one living species. Here is the recorded experience of the man, who, above all others of our time, has triumphantly read the riddle of its manifold pages.