This authority on blood gives us in these lectures many readable and stimulating observations of a clinician and a scholar: a personal presentation, yet free from unduly elaborate hypotheses. He regrets that medical men ignore zoology and botany, which have much to teach us about heredity, constancy of species, and method of development of new species or diseases. The true hereditability of this is to be proved by examining many generations, not a few, for persistent appearance of characteristic traits. New species or diseases occur, he believes, by sudden mutation rather than by gradual selection. To medical men probably the most interesting parts will be those dealing with constitutional (hereditary, endocrine) aspects of specific diseases, such as tuberculosis, grip, endocarditis lenta, hereditary hemolytic anemia with or without jaundice, pernicious anemia, chlorosis, hemophilia, and atrophic myotonia with or without cataract.