EFFECTS OF CARBON* DIOXIDE o.N PROTOPLASM. 15 



As to the cause of these changes, little is known. Heilbronn 

 ('14) and Heilbrunn ('20) have shown that such effects can be 

 produced by changes in temperature, but evidently this factor is not 

 an important one in the cases that have been mentioned. Sziics 

 ('13) showed that aluminium salts could bring about a solidifica- 

 tion followed later by a liquefaction (both reversible) in plant cells, 

 while Heilbronn, and especially Heilbrunn. have obtained striking 

 results with ether, chloroform and other anaesthetics. Important 

 as are these various studies on the effects of chemicals in throwing 

 light on the nature of protoplasm, they give little information as 

 to the cause of the physiological changes in viscosity observed 

 under natural conditions, since the substances employed have not 

 been such as are usually encountered in living cells. 



In the course of some work done on a different problem several 

 years ago the author observed certain effects of carbon dioxide on 

 the protoplasm of living Protozoa which suggested the desirability 

 of testing to what extent this substance might be able to cause 

 reversible changes in protoplasmic viscosity. If it could be shown 

 that it does, in fact, possess such powers in any striking degree, 

 the observation would be a suggestive one, since CXX is not only a 

 universal product of cell activity,. but it has been definitely shown 

 in certain cases (Lyon, '04) to be produced at different rates at 

 different times within the same cell, and a plausible hypothesis 

 might in that event connect the observed changes in viscosity, in 

 part at least, with varying rates of CO 2 production. In the present 

 paper evidence is presented that changes of the sort demanded by 

 such an hypothesis may, as a matter of fact, be produced. 



The material used consisted of the two Protozoa, Paramoecium 

 caudatuin and Colpidinm colpoda, the eggs of the sea-urchin, 

 Arbacia, and in a few experiments filaments of Spirogyra. In 

 addition, a number of observations were made on Ainirba. The 

 consistency of the protoplasm of all of the cells except Amoeba 

 was tested by the centrifuge method of Sziics and of Heilbrunn, 

 advantage being taken of the fact that the more viscous the proto- 

 plasm is, the more difficult it is to bring about a separation from 

 it by means of centrifugal force of solid bodies of different specific 

 gravity contained in it. The cells studied either contained bodies 



