ON THE HEART OE THE DOG. 
155 
emptying into the auricle probably never rises to any important positive value ; indeed, 
according to the experiments of Ludwig, Volkmann, Weyrich, and others, has 
always a mean negative value. The contraction of the auricles, then, must have the 
most important and direct effect upon the work done by the ventricles, and we are 
able to confirm for the Mammalian heart the statement made by Roy (8) for the 
Frog’s heart, viz., “ The work of the heart in the living animal is governed chiefly by 
the auricles, the ventricle influencing the amount of work done only indirectly.” 
In calculating the work done by the left ventricle, we have made no allowance for 
the venous pressure by which the left ventricle was distended. 
A part only, though the much greater part, of the work done at each beat of the 
ventricle, as given in the tables, is owfing to the active contraction of the ventricle 
itself, the other part is proportional to the pressure by which the ventricle is distended, 
and is owing to the elastic reaction of its walls. 
With a desire to learn how great a correction must be made for this factor, as well 
as to find out the maximum pressure in the left auricle with the highest venous 
pressure used, we endeavoured to use upon our hearts the device employed by 
Waller (9) upon Rabbits for ascertaining pressure in the left auricle. 
After the heart was in the warm chamber and going well, the pericardium was slit 
open, the tip of the left auricular appendage seized with a pair of forceps, and gently 
pulled into view ; the appendage was then clamped lower down with a weak clamp 
made especially for the purpose, a slit cut in its walls, and a cannula filled with salt 
solution 0'6 per cent, and connected by a piece of lead tubing, also filled with 0 6 per 
cent, salt solution, with a mercury manometer, was introduced into its cavity and 
firmly tied; the clamp was then removed. 
Of three such experiments tried, two failed, the third was so far successful that the 
results obtained from it can be accejited as approximately correct. The beats of the 
auricle were plainly recorded upon the kymograph paper. 
The outflow from the left ventricle at each venous pressure was estimated in the 
usual way, and was about equal to that obtained from Dogs of the same size in the 
experiments which have been given. 
The results obtained are given in the following table. 
