Jacques Loeb 549 
2. This nfethod has led to the result that the influence of neu- 
tral salts on the swelling of gelatin is of a stoichiometric order. 
Powdered gelatin, when perfused by m/8 or M/4 solution of NaCl, 
shows an additional swelling when afterward perfused by a 
weaker solution of a neutral salt with univalent metal. This 
additional swelling is only possible as long as the weaker solution 
remains below a certain concentration. A comparison of this 
critical concentration for neutral salts of univalent cations with 
univalent and with bivalent anions shows that the limiting molecu- 
lar concentration for the additional swelling is twice as great if 
the anion is univalent as when it is bivalent; regardless of the 
nature of the anion and cation. The facts can be best explained 
on the assumption that the inhibiting effect of the salt upon the 
additional swelling is due to the diminution of the degree of elec- 
trolytic dissociation of a metal-protein compound. If we make 
this assumption, which is supported by the facts known at pres- 
ent, our observations lead to the following conclusions. 
3. Neutral salts with a univalent cation (in concentrations of 
M/8 or M/4) form highly ionizable salts with gelatin. 
4. It seems that these gelatin salts ionize under formation of a 
positively charged metal ion (that of the salt used) and a nega- 
tive gelatin ion which may or may not contain the anion of the 
salt in non-dissociated bondage. 
5. The formation of these gelatin ions causes the considerable 
additional swelling when the gelatin is first treated with the salt 
and then, after the salt is washed away, is exposed to distilled 
water. 
6. The metals of the alkaline earth group form salts with pro- 
teins of the type calcium gelatinate, which are not capable of 
swelling and perhaps little or not at all of ionization. ‘The 
transformation of protein salts with univalent cation (type sodium 
gelatinate) capable of swelling into protein salts with bivalent 
cation (type calcium gelatinate) not capable of swelling ‘is the 
cause of the antagonistic action of the metals of the calcium group. 
7. These results contradict the conclusions drawn from Hof- 
meister’s experiments on the swelling of gelatin and it is pointed 
out that he was misled by a method not suited for the purpose. 
i 
