152 



RELATION OF RESPIRATION TO RHYTHM 



Alcohol. — In concentrations of one-half to one per cent by volume 

 the cardiac ganglion of Limiiliis is markedly stimulated by ethyl 

 alcohoP and may double the rate of heart beat. These concentra- 

 tions of purified absolute alcohol, when added to the standard sodium- 

 calcium chloride mixture do not of themselves modify the color of 

 phenolsulfonephthalein used as pH indicator. In these concentra- 

 tions, however, there results an easily demonstrable increase in the 

 rate of CO2 production by the ganglion, a result which is again in 

 concord with the interpretation that the increased rate of heart 

 beat depends upon the increased respiration in the nerve cells of the 

 ganglion. Table III records the results of some of the experiments 

 with ethyl alcohol as the stimulating agent. 



TABLE II. 

 Rate of CO2 Production by Stretched Ganglion. 



Sodium Chloride. — In the isotonic concentration, m/2, a sodium 

 chloride solution is a pronounced stimulus to the automaticity of the 

 cardiac ganglion of Limulus. The rate of heart beat is promptly 

 accelerated and the individual beats of the muscle merge until a 

 tetanic condition is induced by the continuous discharge of impulses 

 from the ganglionic cells. Determinations of the rate of CO2 pro- 

 duction by the ganglion immersed in m/2 NaCl showed an increase in 

 the rate of respiration of the nerve cells which harmonizes with 

 expectations based on the increase in rate. The rate of CO2 pro- 

 duction was tremendously increased. The averages found in ex- 

 periments with six gangha immersed in isotonic NaCl gave the 



9 Carlson, A. J., Am. J. Physiol, 1906, xvii, 177. 



