294 EXPEllIMENTAL INVESTIGATION OF THE ACTION OF MEDICINES, 



cylinder is one devised by Professor Strieker. One of Marey's 

 cardiographic levers is fixed on a rod close to the side of the 

 animal and some distance above it, and a small piece of cork 

 attached to the lever. One end of a line thread is then fastened 

 to the needle, and its other end pulled through a slit in the cork 

 till it is sufficiently tight to make the lever vibrate with each 

 movement of the needle; it is then fastened by twisting it 

 round the lever, or by a little sealing-wax. If the lever be not 

 raised several inches above the needle, it is pulled too much to 

 a side and not sufficiently downwards to give a good tracing. 

 The tracing may be taken either on plain paper with a glass pen 

 or camel's-hair brush attached to the lever by a piece of cork, or 

 with a dry point on smoked paper. Instead of a vertical 

 cylinder a horizontal one may be used, and is perhaps still 

 better. In this case the lever should be nearly on a level with 

 the needle, and not raised much above it {cf. aiitea, p. 208). 



Is the Quickening of the Pidse due to direct Sti7nulation of the 

 Sympathetic ? — If so, the injection of the drug should cause an 

 increase in the pulse-rate after the vagi have been divided as 

 well as when they are intact. We therefore divide the vagi, 

 inject the drug into the veins, and see whether or not the pulse- 

 rate is increased. On doing this with atropia it is found that 

 the pulse becomes slower rather than quicker, showing that the 

 drug does not stimulate the quickening nerves of the heart 

 The increased rapidity of the pulse which it produces when the 

 vagi are intact i^, therefore, not due to this cause. 



Is the Quickening due to Stimidcition of the Cardiac Ganglia f 

 — The experiment just mentioned shows that it is not, for, if it 

 were, injection of atropia should cause quickening after division 

 of the vagi. Supposing,however, that it had causedquickening,the 

 question whether the acceleration was due to the ganglia or the 

 sympathetic would have to be decided by dividing all the nerves 

 going to the heart with a platinum-wire lieated by electricity, 

 and then injecting the drug, or by applying it to the heart 

 of the frog in a way which I shall afterwards describe. If it 

 quickened the beats of a heart thus separated from all other 

 nerves, it could only do so by acting on the cardiac gaugiia 

 themselves. 



