The statistics designed to measure the degree of inheritance in this disease labour under the cardinal fallacy of assuming that where father and son suffer, the case is one of inheritance, and then proceed to measure the average extent of this inheritance. These statistics are so much waste paper and ink--assuming what they claim to prove. They do not allow for the fact that the child is very frequently exposed in grave measure to infection by the parent; they ignore wholly, indeed, the entire question of exposure to infection, both as regards its extent in time and the virulence of the infection in question. At the present day, discussions as to the inheritance of consumption and tuberculosis in general are not fit for practical application: and a practical disservice is rendered by those who seek to divert public attention from the removable environmental causes upon which the disease mainly depends. We know, for instance, that the incidence of tuberculosis is directly proportional to over-crowding: this being universally true, we must work to abolish over-crowding and to provide fresh air for every one by day and by night. When that is done, alcoholism disposed of, and our milk-supply purified, we may turn to the question of heredity: but the incidence of the disease will then present merely trivial instead of the present appalling proportions. It is not asserted that inherent variations in susceptibility to this disease are not existent. The case would be unique if it were so. But it is asserted that the more we learn of the disease the less importance we attach to this factor, and the more surely do we see that the three syllables constituting the word “infection” substantially suffice to dispose of all the confident dogmas with which we are too familiar. One is almost tempted to quote a forcible phrase of Mill's, and say that, given this point of view, “once questioned, they are doomed.” The only method of accurately studying the question of inherited predisposition would be by comparative study of the resistance of new-born infants as measured by their “opsonic index”--which may be (very roughly) described as the measure of the power of the white cells of the blood to eat up tubercle bacilli.[49] Nor will even this method be free from fallacy. The present writer believes that eugenics is going to save the world; that there is no study of such urgent and practical importance as that of heredity; that if we get the right people born and the wrong people not born, forms of government and such questions will be left even without fools to contest regarding them. Thus he has every bias in favour of emphasising the hereditary factor in tuberculosis. The fact will at least not discredit the foregoing views, which are in absolute accord with those of Dr. Newsholme, our leading authority, in his recent work upon the subject.