From a study of the accompanying tracings we may conclude that:
1. The delicate mechanism of the micrograph registers the movements in the heart and blood-vessels more accurately than does the polygraph.
2. The inertia of the polygraph lever and diaphragm distorts the tracing. The difference between the results obtained with the two instruments is shown by the records made simultaneously with the micrograph and the polygraph.
3. The micrograph is particularly useful for recording heart sounds. Some records illustrating this are shown. We are directing especial attention to this and will report the results in a subsequent paper.
4. While the micrograph will not supersede the polygraph or electrocardiograph, we feel that it has distinct possibilities as a clinical instrument.