The orthodiagram has been a disappointment to those clinicians who had hoped to find an accurate estimation of the size of the heart of vise in diagnosis. Particularly in the field of cardiac neurosis and early myocarditis, in which the ordinary diagnostic methods fail to show any enlargement, evidence of a slight enlargement might be expected to have diagnostic or prognostic import. The roentgenogram does not give us such evidence because of the magnification of the cardiac shadow by the divergent rays and because of the lack of definition at the margin, since the heart is in active motion while the exposure is being made. The orthodiagram, however, gives perfectly definite images of a moving organ, allows of the observation of any anomaly of motion, and depends only on the skill of the operator in the interpretation of the images viewed. In addition it leaves a permanent record of