1010 
DR. W. H. HASKELL ok the rhythm oe the heart of 
auricula*: are, from the commencement of the stimulation, augmented in force (Plate 67, 
fig. 11). The reverse, however, never occurs-—I have never seen quiescence of the 
auricles with simultaneous primary augmentation in the force of the ventricular 
contractions. 
A careful examination of the large number of curves which I possess-will, I venture 
to think, afford clear evidence of the truth of the following statements :— 
1. The effect of stimulation of the vagus nerve, which is most constant, is an augmen¬ 
tation of the force of the contractions, both of the auricles and ventricle; an 
augmentation which cannot be regarded as a mere rebound, so to speak, from a 
previous diminution of the force of the contractions. 
2. In the case of both auricles and ventricle a series of curves can be obtained 
which show that stimulation of the vagus is able to produce a perfect gradation of 
effects upon the strength of the contractions irrespectively of the rate of rhythm : a 
gradation which extends from a simple augmentation of the force of the contractions 
as the result of the nerve stimulation, down to so great a primary diminution of that 
force that the contractions are no longer visible, and therefore quiescence results from 
the stimulation of the nerve. 
3. The auricles and ventricle maybe in different phases of this gradation at the same 
moment, with the qualification that, if quiescence be called the lowest and primary 
augmentation of the force of the contractions, the highest term of the series, the 
ventricle, is always in a lower phase than the auricles. 
The auricular curves are different from the ventricular in one or two other details; 
thus the maximum effect on the force of the contractions is reached more quickly after 
the end of the stimulation in the former than in the latter, so that the auricular beats 
have already reached their maximum, while those of the ventricle are still increasing. 
(Plate 68, figs. 9, 10). The auricles also return to their original force of contraction 
much more quickly than does the ventricle ; as is seen in Plate 68, figs. 9, 10. The 
same figures show another peculiarity of the auricular curves, which is especially 
characteristic of the Toad’s heart, viz.: after the maximum force of contraction has been 
reached, the contractions gradually diminish to a height less than before the stimulation, 
and then again increase up to or slightly beyond their original height: a peculiarity 
which I have never as yet observed in the ventricular curves. 
I have already said sufficient to justify the assertion which I made above, that the 
vagus is never absolutely inefficient ; it always produces some effect or other upon 
stimulation, and I have described a variety of the effects which it does produce. 
Hitherto I have considered the curves as a whole, and have shown that the different 
effects seen when the nerve is stimulated—as far at least as the action of the nerve 
upon the force of the contractions is concerned—can all be arranged in a graduated 
series in which no line of demarcation can be drawn separating one especial effect 
from another. It remains to be seen whether a similar gradation can be produced 
