Note 76 — Chapter IV

Loeb, J., Am. Naturalist, 1915, xlix., 257.

The writer may be permitted to illustrate by a special case his reason for declining to accept Ehrlich’s side-chain theory. Ehrlich and Sachs found that if to a given mass of toxin small quantities of antitoxin are added successively the first fraction added neutralized more than the later fractions; and on the basis of this reasoning Ehrlich concluded that ten different toxins were contained in the diphtheria toxin. Arrhenius showed that the same phenomenon can be obtained when a weak base like NH₄OH is neutralized by a weak acid (e. g., boric acid); hence we should assume that NH₄OH consists of ten different forms of ammonia. Both cases, the satura­tion of toxin with antitoxin and ammonia with boric acid are equilibrium phenomena. (Arrhenius, S., Quantitative Laws in Biological Chemistry, London, 1915.)