775 



atioii of the vagi. One might consider the most plausible explana- 

 tion of our experimental fact to be the following, viz.: that thLs 

 stronger oontratMion of tlie muscle might show itself in an augment- 

 ation of the frequency of its action currents. This explanation how- 

 ever is not consistent. First of all we know the fact already ascert- 

 ained by PiPKH, that the frequency of the action currents in 

 voluntary contraction of human muscles remains unaltered under 

 various strengths of contraction, a fact which one of us (D. DE B.) 

 lately confirmed. But it might be argued, that this fact, though it 

 may be true with regard to voluntary contraction of the human 

 muscle, might not apply to the diaphragm of the rabbit. We, there- 

 fore, tried to get direct experimental evidence on this point by in- 

 ducing a deepening of the inspiratory movements with other methods, 

 f.i. by letting the animal breath an atmosphere rich in CO, or by 

 closing the trachea during a few seconds. It was found that the 

 deepening of the inspiration which follows these procedures is )iol 

 accompanied by an augmentalion of the frequency of the action 

 currents of the diaphragm. We could establish this in many experi- 

 ments; only in one of them we found that after breathing a CO,- 

 atmosphere there was also an augmentation of the frequency of the 

 action currents, hi this experiment we had already performed a 

 local ether anaesthesia of both vagi ; it might be possible that the 

 nerves were still functionally slightly damaged ; anyhow in all our 

 other experiments, in which the increase of inspiration through CO,- 

 breathing preceded the vagotomia, we never found an augmentation 

 by CO,. 



Only one objection must still be taken into account. 



One of the other results of the elimination of the vagi is an 

 acceleration of the iieart. In our experiments, in which the anterior 

 slip of the diaphragm was not detached from the ensiform cartilage 

 for the sake of leaving the muscle in as normal a condition as 

 possible, we generally also found in our curves of the action currents 

 traces of the electrocardiograms of the animal, especially in the cat, 

 where the insulation of the anterior slip of the diaphragm is much 

 more difficult than in the rabbit. These electrocardiograms present 

 themselves under these circumstances as simple, diphasic action 

 currents, which look very miu.'h like the action currents of the 

 diaphragm itself and often cannot be distinguished from them. So, 

 when one counts all the peaks during 0.5 a second, as we always 

 did, a few of these electrocardiograms are always included. The 

 objection might now be made that after the vagotomia through the 

 acceleration of the heart, the number of electrocardiograms is aug- 



