503 
Protoplasm to some Reagents. 
be the surface-tension value of protoplasm based on a value of i for water 
against air. Czapek came to this conclusion because many of the sub¬ 
stances with which he treated cells first began to noticeably affect the 
osmotic properties of the membrane when they were of such a concentration 
as to have a surface-tension value of about 0-685 (against air). He con¬ 
cluded, therefore, that the tension value of protoplasm must be 0-685, and 
that to enter the plasma membrane a reagent must be of a lower surface 
tension. 
All of these theories have been discarded by Warburg ( 26 ), who has 
shown that the degree of toxicity of the methyl, ethyl, propyl, butyl, 
amyl alcohol series is much more closely proportional to the adsorptive 
powers of these alcohols than either to their lipoid solubility or their 
surface-tension values (capillary constants). Warburg arrived at this 
deduction in the following manner: 
If red blood corpuscles (of bird) are frozen the thin cell membrane is 
burst. On thawing, a liquid mass is obtained in which the ‘ solid ’ 1 cell con¬ 
stituents float freely. If this liquid is centrifugalized two layers are obtained: 
an upper, clear, granule-free one, and a lower, cloudy layer containing the 
‘ solid ’ cell particles. If one measures the respiration of the two layers 
separately one finds that only the lower layer respires. From this Warburg 
concludes that respiration depends npon the solid cojistituents op the cell 
( 26 , p. 135). 
Warburg next studied the oxidation of inanimate substances, noticing 
the effect which narcotics have on their ‘ respiration ’. 
Freundlich (8, p. 163) has shown that if an aqueous solution of oxalic 
acid is shaken with blood carbon, there takes place a rapid decrease in con¬ 
centration of the oxalic acid due to adsorption of the acid by the carbon. 
Warburg sought for a possible chemical reaction, and found that oxidation 
of the oxalic acid into carbon dioxide and water takes place. This oxidation 
process can be retarded by narcotics just as can cell respiration. 
In a similar manner, if an aqueous solution of cystin—the sulphur con¬ 
taining amino-acid of egg albumin—is added to carbon and aerated, the 
amino-acid is oxidized into C 0 2 , NH 3 , and H 2 S 0 4 . The same end pro¬ 
ducts are produced as in the case of the oxidation of albumin in living cells. 
This oxidation can also be retarded by narcotics. 
The retardation of these inanimate oxidation processes by narcotics 
rises with the adsorption constants of the narcotics used (methyl-, ethyl-, 
propyl-, and phenylurethane). For example, methylurethane, which is at the 
bottom of the scale with a low adsorption constant, must be of a concentra¬ 
tion of 0-5 mol. per litre to produce a 34 per cent, retardation of oxidation 
of the oxalic acid, while phenylurethane with a high adsorption con- 
1 The ‘ solid’ cell constituents to which Warburg refers are the stromata of the blood corpuscles, 
not solid particles of colloidal size. 
