776 



merited, and that this increase in the number of llie electrocardiogiaiTis 



might be responsible for the augmentation of the action currents 



of the diapiiragm. 



A simple calculation however overthrows fliis objection. Let us 



assume liiat the frequency of the heart in the cat (the same reasoning 



with somewhat other numbers holds true also for the rabbit) is 



about 180 per minute'), ihen there will be present in the curve 



180 

 over a length of 0.5 a second, mostly 0.5 -— -=1:1.5 and at most 



60 



2 electrocardiograms. Supposing that after the elimination of the 



vagi the heart accelerates from 180 to fi. 240 or even 360 beats 



per minute, an acceleration of lOO"/,, which will only be seldom, 



if ever, present, then we can expect to find in our curves over 



360 

 0.5 a second 0.5 ^— - :^ ,i electrocardiograms, i.e. an apparent 

 60 



augmentation of mostly 1 or at utmost 1.5 per 0.5 second. So this 

 would give an ap|)arenl augmeiilaiion of the frequency of the action 

 currents of the diaphragm of 2 or 3 per second. Fiom (his reasoning 

 it is clear that even with these numbers, which we look as un- 

 favourably as possible, this factor, which undoubtedly exists, cannot 

 explain the augmentation present in our experiments. 



We think it therefore permissible to conclude that for the greatest 

 part, the augmentation of the frequency of the aclion currents of 

 the diaphragm after elimination of both vagi \h due to the ele7nination 

 of the centripetal impu/ses, m/u'c/i noriiially travel aluDg the vagi to 

 the central nervoiLS si/.itein :tntl obvionxly e.rert an inhihitory influence 

 0)1 the respiratory movements, at least in the cat and the rabbit. 



Since the researciies of Hehing and Breukh it is wellknown that 

 centripetal vagal impulses have an important influence on the respirat- 

 ory movements, especially on the inspiration. The fact shown by 

 our experiments gives clear and, as far as we know, until now 

 unknown evidence of this influence. 



September 1923. Physiological Laboratory of the 



University of Utrecht. 



') This assumed number is on the high side; for a smaller number our reasoning 

 becomes yet more conclusive. 



