A comparison between the action of carbonic acid and other acids upon the living cell

Summary

Experiments on the comparative influence of CO₂ and other acids upon the living cell, carried out with two objects (Paramaecium caudatum and the hairs of the anther filaments ofTradescantia virginica) have shown the following:

• 1. The different toxicity of CO₂ and of other acids does not only depend on the different rapidity of their penetration (which in a number of cases is considerably higher than in other acids), for with an equally rapid penetration into the cell, the toxicity of these acids can be different.

• 2. According to the degree of their toxicity the investigated acids can be divided into two groups: I — including the mineral acids, citric acid and oxalic acid; and II — to which belong CO₂ and the acids near to it, easily penetrating into the cell, valerianic and acetic acids, which are more toxic, although their pH is the same as in the I-st group.

• 3. The toxicity of the second group of acids does not depend on their pH, but on the concentration of the undissociated molecules, as their effect is the same with a considerably less acid pH, than that of the acids of the first group.

• 4. Carbonic acid stands by itself among all these acids, because of its narcotic action, which apparently depends on the CO₂ molecule. The other acids are not able to cause narcosis.

• 5. Taking all this into consideration, carbonic acid can be characterised as an acid penetrating more easily into the cell than the other acids, acting as an acidifier in small doses, as a lethal agent in higher ones. Its penetrative and lethal properties do not depend on the H-ion concentration, but on the CO₂ molecule. The narcotizing capacity is particularly characteristic for CO₂ and creates a sharp difference between it and other acids.