44 ELECTROCARDIOGRAPHS; BALLISTICCARDIOGRAPHS; ELECTROMANOMETERS; METABULATORS INCLUDING MOUTHPIECES, NOSE CLIPS, BREATHING TUBES, THERMOMETERS, CARBON-DIOXIDE CONTAINERS, CHARTS, SCALES AND SLIDE-RULE CALCULATORS THEREFOR; ELECTRIC-SIGNAL ELECTRONIC RECORDERS AND RECORDING SYSTEMS OF BOTH THE SINGLE AND MULTI-CHANNEL TYPES FOR RECORDING PHYSIOLOGICAL AND RELATED PHENOMENA, AND WRITING ARMS AND TYLI THEREFOR; ELECTRODES AND STRAPS AND PASTE FOR USE WITH THE FOREGOING; AND ELECTROPHRENIC RESPIRATORS