CARBON DIOXIDE AS A NARCOTIC AGENT. 451 



Inasmuch as carbon dioxide is a normal product of metabolism, 

 an understanding of its characteristic effects on living cells and 

 the mechanism by which they are produced is of importance. Un- 

 fortunately, most of the studies previously made on its action have 

 been concerned with entire organisms where numerous complicat- 

 ing factors prevent the separation of its more characteristic effects 

 from others of a less fundamental nature. It is the object of the 

 present paper to study in a quantitative way certain aspects of the 

 narcotic effects of carbon dioxide on single cells the developing 

 egg cells of Arbacia where complicating factors are reduced to 

 a minimum. In particular, an attempt has been made to deter- 

 mine the extent to which such effects are reversible. A second 

 paper * deals similarly with a simple tissue the striated muscle of 

 the frog and studies upon ciliated epithelium are to be reported 

 elsewhere. 



For quantitative work, the developing egg of Arbacia proves 

 very satisfactory. Since favorable material shows about 100 per 

 cent, division under normal conditions, any delay in the occurrence 

 of the first cleavage may be measured and used as a suitable quan- 

 titative criterion for narcotic or toxic effects upon the activity of 

 the cell. Smith and Clowes (1924) have studied from a somewhat 

 different point of view from that of the present paper the effects 

 of carbon dioxide upon the cleavage of echinoderm eggs and have 

 found that development is inhibited by CO 2 at pH values which 

 in its absence are without effect upon cleavage. The present ex- 

 periments differ in at least two respects from those of Smith and 

 Clowes. In the first place, they have to do with exposures of 

 varying lengths followed by a return to normal sea water to per- 

 mit a determination of the extent to which the effects produced are 

 reversible. In the second place, a different method has been used 

 for the quantitative measurement of the degree of retardation of 

 the developmental processes. Instead of measuring the total num- 

 ber of cell divisions secured in a given time irrespective of whether 

 they be the first, second, or third, the quantity here measured has 

 been the time required for the first cleavage in each case. Furth- 

 ermore, this has been done in such a way as to take into account 



1 Amer. Journ. PhysioL, LXXXII., 241. 



