166 



INHIBITORY NERVES AND CO2 PRODUCTION 



noted that the rate at which the color change progressed was more 

 rapid toward the end of a determination when the ganglion was 

 presumably gradually escaping from inhibition. 



In preparations showing a low initial rate of CO2 production it is 

 easy to depress this rate by inhibition for a much longer time than 

 with vigorous preparations. In one experiment (not tabulated) no 

 color change was noted at the end of 30 minutes of inhibitory nerve 

 stimulation, although subsequently the normal rate of 5 minutes was 

 restored. These observations are in complete harmony with what we 

 know about inhibition of the contraction rate in this form.^ 



TABLE II. 



Efed of Strength of Inhibiting Stimuli on Time For CO2 Production. 



Since strong stimuli applied to the inhibitory nerves of the heart 

 produce a greater slowing of the rate of heart beat than weak stimuli, 

 experiments were made to see whether they produce a similar effect 

 upon the rate of CO2 production in the ganglia. Some typical experi- 

 ments are given in Table II. 



The results leave no doubt that the stronger inhibiting stimulation, 

 which is known to produce a slower heart beat, also causes a greater 

 depression of the rate of the chemical processes in the ganglia which 

 give rise to the formation of CO2. 



If we view the entire process of inhibition we may represent the 

 experimental results graphically as has been done in Fig. 1 which is 

 constructed for four of the experiments in Table I. The graph shows 



4 Carlson, A. J., Ayn. J. Physiol, 1905, xiii, 217. 



