MICHIGAN ACADEMY OF SCIENCE. 
61 
The catalyst does not initiate a reaction, but merely increases the 
rate of one already in progress. On the other hand, ferments will 
initiate reaction which are not already in progress. Soluble starch, 
under suitable conditions, can be kept without appreciable cleavage, yet 
when treated with saliva a part of it is immediately split into the 
simple sugars. In this respect the catalysts and the enzymes are not 
alike, for the enzyme does not necessarily enter into a reaction already 
in progress, but actually initiates one. 
Again, the catalyst does not enter into the reaction, but facilitates 
the final result by its presence. This would not appear to be so in 
regard to the starch splitting ferment of the saliva, for, in normal saliva 
we find about 5 parts of free ammonia per million. If, however, 10 cc. 
of saliva is treated with 25 cc. of a 1 per cent soluble starch solution 
the ammonia is increased by about 20 part per million. The experiment 
bearing on these findings consisted in the estimation of the ammonia 
content in 5 treated and 5 untreated specimens of saliva. In those un- 
treated there were from 3 to 9 parts of free ammonia per million, while 
in those treated there were from 20 to 27. This increase in ammonia 
unquestionably has its origin from the protein molecule. As a further 
evidence of protein cleavage in the process of splitting starch, we find 
that untreated saliva does not readily conduct an electric current, while 
the treated saliva gives but little resistance; this is, of course, due to 
the increased ionic content. From these experiments it would seem 
that the cleavage of starch by ptvalin is not due to the mere presence of 
the ferment, but that there is an actual chemical reaction more than 
catalytic in nature. Tt is, possible, however, to account for the protein 
cleavage if we consider the starch splitting process one of autocatalysis. 
In applying this hypothesis it is necessary to assume that the active 
ferment — as such — does not exist in the untreated saliva, but is present 
as a component of the protein molecule in the proferment stage. To 
activate the ferment the soluble starch may act as a catalyzer. As a re- 
sult of this catalytic action, the ferment is split from the protein of 
the saliva, and as other products of the reaction there is formed free 
ammonia, neutral salts, etc. Now, the free ferment being a product 
of this catalytic process, reacts autocatalytically as a starch splitting- 
ferment. The double reaction may be represented as follows: 
Ferment + Cleavage products 
! Soluble starch Protein molecule (proferment) 
(Salivary protein) 
Simple sugar 
Cell ferments, in contradistinction to inorganic catalysts, are in gen- 
eral supposed to be destroyed by heat. Our experiments with saliva, 
however, show that the ferment is not destroyed by short exposures to 
high temperatures, although it is rendered inactive. If saliva is 
boiled for a short time, then dialyzed in distilled water, and at intervals 
a portion is removed and tested, it is found that it is reactivated in 
