MICHIGAN ACADEMY OF SCIENCE. 
63 
saturated before the ferment passes to the exterior. Inasmuch as the 
ferment of the filtered saliva dialyzes much more rapidly than that of 
the unfiltered we may conclude that the ferment itself is not so strongly 
colloidal in nature as are the other constituents of the saliva which 
are removed by filtration. This experiment though not at all proving the 
crystalloidal nature of the starch splitting ferment of the saliva, at 
least tends to show that after removal by filtration of certain salivary 
constituents the ferment more nearly resembles a crystalloidal com- 
pound than heretofore recognized. 
Pepsin also may pass through a thin collodion sac. This fact may 
be proved by the following experiment: A solution of pepsin hydro- 
chloric acid is placed inside a collodion sac; this is surrounded by a 
hydrochloric acid solution of the same strength. Cubes of boiled egg- 
white are then added to the outside solution. As control, egg-white 
cubes are placed in the same percentage of hydrochloric acid in a 
separate container. That the pepsin diffuses to the exterior is shown 
by the digestion of the egg-white in from 30 to 40 hours. The egg-white 
in the control remains intact. From the results of similar experiments 
Barendrecht advances the theory that enzymes are radio-active bodies, 
the chemical action being due to radiation. By a series of experiments, 
however, it is shown that the ferment penetrates the membrane. 
The inorganic catalysts have the property of continuing a reaction to 
its completion. In contradistinction to this the ferments are active in 
their cleavage process, at least in vitro, only to a partial extent. Here 
we have a distinct difference between catalyst and enzyme. The one 
completes the process; the other does so only partially. 
Another characteristic of ferments not manifested by catalysts is 
their property of causing a reversible action. For instance, although 
emulsin splits amygdalin, a plant glucoside, into benzaldehyde, hydrocy- 
anic acid, and glucose, it is also capable, to a certain extent, of synthe- 
sizing these separate components into amygdalin. In eitnher case — 
analytic or synthetic — it is a question of approaching an equilibrium. 
The action of fermentation may be explained by the supposition that 
the ferment solution is a specialized ionic arrangement which induces 
rapid autolysis of a complex molecule. The specific ionic content of 
the ferment solution may be responsible for an instantaneous break 
in the equilibrium of the complex molecule acted upon. As the char- 
acter of the red blood cell is immediately lost — the hemoglobin going 
info solution — when treated with distilled water ; and as the complexity 
of the protein molecule is partially lost — the neutral salt, alkali, and 
amino-acids splitting off — when small quantities of blood-serum, for 
instance, are treated with several times their volume of distilled water; 
so also can we assume that there is a similar relation — though far more 
complex in nature — between ferment and substrate? 
May not, however, the real solution of this problem depend upon the 
isolation and thorough study of the ferment complex, if such exists. 
