The presence of the tubercle bacillus, a local injury of tissue and diminished bodily resistance are accepted as a necessary trio of conditions which determine tuberculous infection. Clinicians for many centuries have recognized the third factor as important, while the first two have been accepted only in the present age of exact pathology. It is the hope of the modern student so to analyze the elusive complex of bodily or general resistance as to put preventive medicine, as applied to the individual, on a sound basis.
One method of attacking this problem is to determine the functional changes which accompany or facilitate infection. In tuberculosis, the functions of the special tissue affected, of nutrition and of the circulation suffer chiefly. Of these three the local repair and correction of the error in nutrition are so dependent on efficient circulation that study of the functional errors of the cardiovascular system