the ratio to the whole is 1 : 33965, which is very near the former result. In slower pulses it is not easy to find an origin for the risef, but if, as must be the case when the pulse is at 40 (its limit of slowness), the arterial tension is at its maximum, the rate of closure of the aortic valve must be at its maximum also, and the whole first part almost entirely occupied by the true systolé. When such is the case the equation xy=kx with k = 22 is satisfied by y being equal to 3·46 (about), which is curiously near the relation found in quick pulses, and tends strongly to shew, though these are all the grounds for it, that the length of the systolé of the heart is always a definite part (th) of the whole pulsation, whatever its rate. The traces from which the preceding observations have been made were all taken on myself, and the repetition of them by others at different rates of pulse would be a means of verifying or a cause for rejecting the results arrived at. The chief sources of error in finding the ratios given above, lie in the watchwork, which if not going at an exactly similar rate each time it runs, gives the rapidity of the heart incorrectly. Also, on starting, its speed augments for a short time and then decreases, both which cause variations from the true results. By taking a trace after having remained some time in the hot room of a Turkish bath very rapid pulses can be recorded, up to and above 150 a minute in health, without the least inconvenience. Very slow pulses can be produced by lying nude some time in a cold air, or by drinking iced water, especially when nude. DESCRIPTION OF THE FIGURES. They were all taken one half the size here represented. Except Fig. IX. they read from left to right. Fig. I. Apex trace of a heart beating 125 times a minute. Fig. II. Trace of a heart beating 125 a minute, an inch internal to the apex beat. Fig. III. Apex trace of a heart beating 88 a minute. Fig. IV. Trace between 6th and 7th ribs, below the apex, of a heart beating 88 a minute. Fig. V. Fig. VI. Apex trace of a heart beating 76 a minute. Apex trace of a heart beating 50 a minute. Fig. VII. Apex trace of a pulse of 90 a minute, taken with a lever 2 inches long, attached to the sphygmograph pad by a thread. Fig. VIII. Apex trace of a pulse at 60 a minute, taken when the body was inclined forward. Fig. IX. Apex trace of a pulse at 42 a minute. It reads from right to left. Fig. X. Apex trace of a pulse at 103 a minute, prepared for measuring. |