ON THE HEART OF THE DOG. 
157 
cases this increased pulse-rate was accompanied by a greater velocity, in other cases 
by a smaller velocity of the blood stream. 
Vierordt found with reference to the relation between pulse-rate and what he 
calls the “greatness of the systole,” i.e., the quantity of blood thrown out at each 
systole, that sometimes, perhaps in most cases, a diminished pulse was accompanied 
by an increase in the greatness of the systole, while on the other hand cases were 
observed in which the reverse happened. The relative greatness of the systole was 
determined from the number of beats which occurred in the time necessary for the 
completion of a circulation. 
In our experiments we increased or diminished the pulse-rate by raising or lowering 
the temperature of the blood flowing into the heart, using for this purpose the same 
method as that described by Professor Martin (Phil. Trans., 1883, p. 663). 
We give below the records of two experiments. 
In the experiment of May 18 a low venous pressure, 20 centims., was used, and 
besides the thermometer in the inflow tube, another was placed in the left subclavian 
artery, the bulb projecting into the aorta. The temperatures were read from both of 
these thermometers at the end of each observation ; in the table the temperature on 
the arterial side is marked A, that on the venous side V. After observation 18 of 
this experiment, one of the supply flasks unfortunately ran completely empty, 
allowing some air to get into the heart, so that the succeeding observations could not 
be trusted. In the experiment of May 30 a venous pressure was used of such a 
height that, judging from our other experiments, the maximum outflow at each 
systole for the given pulse-rate was obtained. 
In this case a thermometer was not placed in the subclavian artery, since it would 
have interfered to some extent with the flow from the left ventricle, and owing 
to the rapidity with which the flasks were emptied, we were not always able to get 
the temperature of the inflowing blood, nor the times of the observations ; these latter 
however were made at intervals of from one to three minutes. 
