FROM THE HUMAN CHEST-WALL. 25 
: éoutained in the whole, or the z by the y, when 2 is the required 
zy 
result. 
Thus 41 x 34125 = 139-9125, say 140; 
141 x 1832 = 258312; 
and /41 = 6°4, about; /141 = 11°88, about; 
and : 6-4: 11°88 :: 140 : 259-9, about; 
which is very near the required numbers. 
If zy varies as the square root of z this can be stated thus 
ay = k./z; k being a constant for any given position. Taking one of 
the above cases, z equalling 41, zy = 140; consequently k = 22 nearly, 
which includes, within the limits of experimental error, all the measure- 
ments that have been made of traces taken while lying. When sitting 
or standing the results are not quite so uniform, as may be seen in the 
table, on which the equation curves have been drawn with k = 22, 
and also = 20: the latter, the lower one, passes through or approaches 
. most of the sitting and standing observations. 
To find the duration of the ventricular systolé is very important, 
but not at all easy in many cases. In all rapid pulses, measuring from 
the commencement of the main ascent to the point from which the 
rise f originates, and which can scarcely be anything but the termina- 
tion of the systolé, it has been found that that interval is contained 
3°4 times in each revolution. In Fig. IV the trace of 87°5 a minute 
(rare from being very detailed), it is found that between the same 
points the ratio tothe whole is 1 : 33965, which is very near the former 
result. In slower pulses it is not easy to find an origin for the rise f, 
but if, as must be the case when the pulse is at 40 (its limit of slow- 
ness), 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 zy = k./z 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 show, though these are all the grounds for it, 
that the length of the systolé of the heart is always a definite part 
(23th) 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 
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