Abstract: From the foregoing account one can see that determined efforts have been made to identify sources of error in the force ballistocardiogram as a record of the resultant of the forces generated by the heart. In few other clinical methods has there been such an extensive hunt. Certainly nothing of much moment has turned up, although we found reason to believe that differences in vessel elasticity and in size of subject would have some effect on the relation between the record and the forces which originate it. An effect of the position of the heart and of arteriosclerosis would manifest itself only if the deviation from the normal was extreme. While various other uncertainties certainly exist, it seems unlikely that they are important. Clinicians are often forced to use methods which are not perfect and much trouble can be avoided by proper care in the preparation and use of normal standards. In the case of the ballistocardiogram the scatter of the normal population will be due not only to differences in the forcefulness of the hearts of healthy persons, but also to all the other factors which might have some effect on the proper recording of such forces, such as: differences in body size, body habitus, blood pressure, arteriosclerosis and the usual technical errors. But if we identify as abnormal only those outside the statistical limits of normality of such a healthy group, the odds are strongly in favor of a valid identification of abnormality of the cardiac forces. Using the data from the cadaver experiments as a test, one finds we can identify the magnitude of the acceleration of the blood with an accuracy about equal to that of the common clinical method of taking blood pressure. It is true that the Riva-Rocci method has greater errors inherent in it than most doctors realize; the point I wish to make is that despite such errors, much important clinical information has been secured by means of it, and its introduction into clinical medicine was responsible for a great advance. I am hopeful, therefore, that the time has come when doctors will no longer be content to regard heart diseases from the purely anatomic viewpoint, and when a statement of the strength and coordination of the heart's contraction will be considered an essential part of the record of every cardiac case. The ballistocardiogram provides a method of readily securing information on this point without causing the least discomfort to the patient.