1905] BARNES—THE THEORY OF RESPIRATION gi 
not undergo direct oxidation but hydroxylation, i. e., its hydrogen 
atoms are successively replaced by hydroxyl radicles, with conse- 
quent splitting into various intermediate products, such as carbon 
monoxid and hydrogen peroxid, carbonic acid and water being the 
end products. ARMSTRONG says: 
There is little reason to suppose that changes take place at high temperatures 
in rapid combustions in ways very different from those in which they occur at 
lower temperatures... . . The effective operation is not the mere blow due to 
impact or the vibration caused by this in the molecule, but the conjunction of 
compatible molecules and the consequent formation of composite systems within 
which change can occur. In so far as temperature influences the formation of 
compatible systems, either as regards their character or the rate at which they 
arise, temperature has an influence, but probably not otherwise. 
I ask you to notice, then, that the process of combustion is now 
being interpreted in the light of changes like those which have long 
been known in organisms under the name of hydrolysis, and are 
the characteristic mode of action of enzymes. Thus, when starch is 
acted upon by diastase it is probably by repeated reactions between 
water, dissociated into hydrogen and hydroxyl groups, and oxygen— 
in other words, by continued hydroxylation—that it becomes ready 
to fall apart into a series of dextrines and finally into maltose. Dias- 
tase in some way facilitates this dissociation. Maltase takes up the 
task, and maltose, further hydroxylized, cleaves into two molecules 
of glucose. Then zymase may lend its aid and hydrolyze the glu- 
cose molecule into lactic acid, breaking the latter still further into 
carbon dioxid and alcohol. 
The mechanism of the digestion of starch is not known in detail, 
though the various intermediate products have been fairly well 
studied. The usual assumption made is merely that water com- 
bines with the starch under the action of diastase. I have carried 
the theory a little further into detail, as seems warranted by the 
studies of combustion. It is worthy of note also that the late steps 
in the process, the hydrolysis of glucose by zymase, have been desig- 
nated by the term ‘‘fermentation.’”? The combustion of starch has 
likewise not been examined, but as the end products are identical 
with those of digestion, it is not at all improbable that the inter- 
mediate steps are the same, though they succeed one another too 
fast to be followed by means at present available. 
I need hardly remind you that our present ideas of the dynamics 
