112 



PKACTICAL PHYSIOLOGY 



CHAPTER XXX. 



THE EFFECT OF NICOTINE, CHLOROFORM AND ETHER UPON 



THE HEART. 



Action of Nicotine. Dissect out the vago-sympathetic and record 

 the beat of the heart by the suspension method. Record the effect of 

 excitation of (1) the vago-sympathetic, (2) the crescent. Now apply 

 to the heart a few drops of a 1 per cent, solution of nicotine. The 

 frequency of the heart is at first lessened and then slightly increased, 

 for the nicotine firstly excites and secondly paralyses the synapses of 



Fio. 110. Contraction of the frog's heart. I. Normal heart-beat. If. and III. poisoned 

 by nicotine. The downstroke represents contraction. The time is marked in seconds. 

 See footnote, p. 98. (L.H.) 



the vagus fibres with the cardiac ganglia. These ganglia contain the 

 cell stations of the vagus fibres. Stimulation of the vago-sympathetic 

 trunk no longer produces inhibition, but augmentation and acceleration. 

 The cell stations of the sympathetic fibres are in the third sympathetic 

 ganglion. 



