Annual Address by the President. 
15 
lability of the plasma proteids is caused by the presence of aldehyde 
and amido-groups within the same molecules. * * * The 
primum movens in the living protoplasm must be defined as a mode 
of motion of labile atoms in the plasma proteins ; that is, as a spe- 
cial case of chemical energy ” According to Loew, the enzymes 
belong to the dynamically labile compounds. 
While .the chemical structure of the enzymes is not yet known 
the researches of Emil Fischer go to show that a knowledge of their 
constitution is not far beyond our reach. In the fermentation of 
the sugars Fischer 13 has shown that the enzymes can only “attack 
those sugars which possess a molecular configuration correspond- 
ing to their own/ 5 — ’that is, they must fit each other “as the key 
fits its lock.” Viewing the enzymes as nucleo-proteid bodies, and 
as being optically active, he reasoned that their molecules must 
have an asymmetric structure. Their selective action toward a 
and 13 methyl-gluoosides strongly supports this view. 
According to Fischer, two methyl-glucosides are formed by the 
action of hydrochloric acid (HC1) bn a solution of d glucose in 
methyl alcohol, and their configuration is given as follows : 
H.C.O.CHg 
! CH.OH 
O CJH.OH 
\ I 
X CH 
dm . oh 
CH,OH 
OH 3 .O.C.H 
j CH.OH 
O CH.OH 
X CH 
CH.OH 
CH.OH 
One is called a, the other /?, and their difference is found in the 
configuration of the one asymmetric carbon atom, yet the enzymes 
which attack the « will not attack the (3, and vice versa. This 
important discovery sheds a world of light upon the vexed problem 
of fermentation, and will therefore help to explain many of the 
obscure phenomena of diseases and of immunity. It will also find 
a place in the investigation of many of the difficult problems of 
physiological chemistry. A very admirable feature of FischePs 
hypothesis is its capacity to receive aid from, and give aid to, several 
other hypotheses — it possesses a wide range of applicability. 
In 1892, our esteemed colleague, Professor J. W. McLaughlin, 14 
in his book on “Fermentation, Infection and Immunity,” elabo- 
rated a “Physical Theory,” a quotation from which is here pre- 
sented. After developing the modern conception of complex mole- 
cules, Dr. McLaughlin goes on to say : “When we add to this con- 
ception of atomic and molecular union, that of atomic vibrations 
