1008 
DR. W. H. GASKELL 03ST THE RHYTHM OF THE HEART OF 
longer possible to speak of the inhibitory action of the nerve apart from its whole 
action. In every case, then, it will be necessary, before we can assert that its action is 
abolished, to determine that the vagus is no longer able to cause any alteration, not 
only in the rate of rhythm, but also in the strength of the cardiac contractions. 
I use the term alteration , rather than diminution , of the force of the contractions 
advisedly, for it will not be sufficient to show that the vagus is no longer able to cause 
any diminution; it must also be shown that it is unable to cause any increase of the 
force of the beats, because, as will be seen, the most permanent and invariable function 
of the vagus (in the heart removed from the body, at all events) is to increase the 
strength of the muscular contractions. 
Before describing the results of the experiments upon which the assertions made 
above are based, it is desirable to say a few words about the conditions under which 
they were conducted. In every case the vagus nerve was carefully dissected out nearly 
or quite up to its ganglion and placed on the electrodes, so that there was about a 
quarter of an inch of free space between the electrodes and the nearest tissue. The 
experiments were made in the months of February, March, April, May, June, and 
July of this year, and the animals used were Toads or large, in most cases freshly 
caught, specimens of Rana temporaria. The left vagus was invariably used, and I can 
safely assert that in no single instance has its stimulation failed to produce some effect 
upon the heart, although, as will be seen, that effect is not always the same. 
In my first experiments the heart was suspended by means of Kronecker’s forceps 
attached to the bulbus aortse, the ventricle was slit open from base to apex, and the 
contractions of the ventricle alone were registered by means of a lever which was 
attached by a thread to the very apex. The typical effect of vagus stimulation under 
these circumstances is seen in Plate 67, fig. 4, which shows that by this method 
complete inhibition can be obtained ; that when the ventricle begins to beat again the 
first beats are very small, but that they soon begin to increase in size and shortly after 
the end of the stimulation reach a maximum which is very muchgreater than be for 
the stimulation. From this maximum the force of the contractions very slowly 
diminishes to the original size. 
I give this curve simply to'show that the nature of the phenomena seen upon vagus 
stimulation when the clamp is used cannot be ascribed to the use of the clamp, for, as 
the subsequent curves will show, there is no essential difference between the curves 
produced whether the clamp is absent or present. As, however, the results are much 
more interesting when the auricular and ventricular beats are simultaneously recorded, 
I will proceed at once to describe the effects of stimulating the nerve when the clamp 
is in the auriculo-ventricular groove and is tightened so as just to hold the tissue ; the 
ventricle is therefore beating synchronously with every beat of the auricles. 
As the large majority of my experiments have been made with the clamp in this 
position, I am enabled to draw conclusions from a very great number of curves, each 
one of wdiich represents a separate stimulation of the vagus nerve. Upon examination 
