DOSAGE OF THE MAMMALIAN HEART BY CHLOROFORM 71 
employed were straw, and were armed with writing points in the following way : A 
piece of" capillary glass tubing was bent 90° at three places, and one arm of it inserted 
into the cylinder of the straw so as to lie as it in a longish groove along it. A little 
piece of very fine wire was attached to the lower free-hanging end of the pen, and 
could be bent with tweezers, so that, by altering the centre of gravity, the tip of the 
pen could be made to press in any desired degree upon the blackened travelling paper. 
Electrodes upon a ball and socket joint were arranged so as to be applicable 
to the cardiac nerves. Arrangement was also made to faradize the heart wall. A 
diffuse electrode was fixed as a plate against the moist extra cardiac tissue above the 
base of the heart in the upper clamp ; the condensed pole was formed by a minute 
hook inserted into the ventricle in its upper third ; a very thin wire brought this 
hook into the circuit. In both cases the electrodes were fed by an inductorium 
served by a Daniell cell ; the moment of application of the faradizing current was 
indicated on the graphic record automatically by an electro-magnetic signal. Time, 
either in second or in five-second intervals, was likewise automatically recorded. 
The fluid flowing from the heart was collected and measured when desired. 
The solution we employed throughout was the modification of Ringer's 
solution devised by Dr. Locke. 5 We should probably never have attempted to 
work upon the isolated mammalian heart had we not witnessed, at the International 
Congress of Physiologists at Turin, two years ago, Dr. Locke's admirably successful 
demonstration of the effect of glucose upon the ventricular beat of the isolated rabbit 
heart. We therefore adopted His modification of Ringer's salt solution with some 
confidence that it might succeed in keeping active the heart of the cat, isolated under 
appropriate conditions. The cat is with us a much cheaper object of study than the 
rabbit, hence, since we desired a considerable number of observations, we preferred to 
employ it. The modified Ringer's solution has, in fact, fully answered our 
expectations. We have not added glucose to it, preferring for our initial observations 
to use the simplest solution possible. It, without the glucose, suffices to support, if 
duly oxygenated, the activity of the cat's heart for the greater part of a working 
laboratory day. We refer to the solution as ' modified Ringer's ' in the present 
Report, because by ' Locke's solution ' might be understood a glucose containing 
saline solution ; but, as a fact, it is Dr. Locke's solution that we have invariably used, 
omitting only from it the glucose. Locke's modified Ringer's solution has the 
following composition' : — NaCl, 0-9 per cent. ; CaCl„ 0*024 P er cent - '■> KC1, 0-042 
per cent. ; NaHCO,, o - oi per cent, in distilled water. 
The amounts of chloroform that were measured in preparing the dilute 
solutions were sometimes small. In the earlier experiments, these, as well as the 
larger doses, were measured by volume at the room temperature I4°-i6° centigrade. 
For these measurements we employed a burette divided into hundredths of a cub. 
centimetre, provided with a stop-cock, and armed for delivery with the capillary 
