CIRCULATION OF THE BLOOD. ~ 85 | 
never struck me as peculiarly insignificant, though it has peculiarities, 
to be mentioned. immediately. 
The ankle-trace of a pulse at about 70 a minute, as taken with an 
ordinary sphygmograph, differs from that at the wrist in more than Page 147. 
one point. The primary rise, as previously mentioned, is less abrupt ; 
the following fall is more considerable, and is not broken by the notch 
nearly constantly seen in wrist-traces of this rapidity. The secondary 
rise starts from a lower level and is well marked, reaching its climax 
considerably nearer the next primary rise than in the wrist-trace. There 
is, however, another feature in the early part of the secondary rise in 
‘the ankle-trace, which deserves special attention because of its general 
occurrence. As is well known, in wrist-traces the secondary rise com- 
mences promptly and is quite uniform in character, but in ankle-traces 
there is nearly always a short horizontal continuation of the curve im- 
mediately following the primary fall, the point of departure of the 
two lines being clearly indicated by an abrapt, though not consider- 
able, change in direction. This horizontal portion of the trace is not 
of any considerable length, being im a pulse of 70 a minute about one- 
eighth of the whole beat; it is followed by a well-defined secondary 
rise, which is much longer and more gradual than the primary. 
Though described above as horizontal, this short interval between 
the two undulations is not so always, being frequently slightly 
oblique, sometimes in one direction, sometimes in the other. When 
its curve is downwards (that is, when it tends in the same direction 
as the primary fall), it may appear to be part of that event, which 
would then look as if broken; when its curve is upwards (that is, 
when it tends in the same direction as the secondary rise), it makes 
the trace appear more normal in comparison with that from the 
wrist. 
Having now explained the ankle sphygmograph-trace, in consider- 
ing the simultaneous wrist and ankle traces, it will be necessary to 
commence with the description of the instrument employed to obtain 
them.- A drawing from it above is seen in Plate III, fig. 1, from the 
side in fig. 2, and a double sphygmogram is given in fig. 4. 
The double sphygmograph is constructed from two of the ordinary 
sphygmographs of Marey, as first constructed by Breguet. One, that 
‘employed in taking the ankle-trace, retains all its original parts, 
except the side lappets for fixing it to the arm, and its recording- 
apparatus receives the double trace. A second lever is fixed in con- 
nexion with it by two uprights so placed as to allow the axis of the 
second lever to be parallel to and above the one belonging to the 
instrument, sufficient room being left to allow the latter to move un- 
obstructed up to the top of the recording paper. This second lever, 
which is a fac simile of that used in the sphygmograph, is placed so 
