ARTIFICIAL RHYTHM. 205 



Over the tissue I lowered an inverted beaker filled 

 with the gas the effects of which I desired to 

 ascertain, and by progressively forcing the rim of 

 the beaker into the water I could submit the tissue 

 to various pressures of the atmosphere of the gas 

 I was using. By an appropriate arrangement the 

 electrodes passed into the interior of the beaker, 

 and could then be manipulated from the outside, so 

 as to be properly adjusted on the tissue. In this 

 way I was able to observe that different gases 

 exerted a marked influence on the rate of the 

 artificial rhythm. 



The following table gives the ratios in the case 

 of one experiment : — 



Rate of artificial rhythm, 

 in air. 



36 per minute. 



In oxygen. 

 50 per minute. 



In carbonic acid. 

 25 per minute. 



It may here be observed that to produce these 

 results, both carbonic acid and oxygen must be 

 considerably diluted with air, for otherwise they 

 have the effect of instantaneously inhibiting all 

 response, even to the strongest stimulation. When 

 this is the case, however, irritability returns very 

 soon after the tissue is again exposed to air or to 

 ordinary sea-water. But I desire it to be under- 

 stood that the results of my experiments on the 

 influence of oxygen, both on the natural and on the 

 artificial rhythm, have proved singularly equivocal ; 

 so that as far as this gas is concerned further 

 observations are required before the above results 

 can be accepted as certain. 



I have still one other observation of a very 



