July 27, 1912
There are few persons who have the facility of expressing a somewhat abstract scientific conception in terms of an analogy that strikes home at once. Emil Fischer furnished an admirable illustration of what we have in mind when he elucidated, by a now famous phrase, the specificity of enzymes, that is, the capacity of digestive ferments to attack one substance and not another which may even be closely related. Enzyme and substrate, according to Fischer, bear a relation to one another like that of a key to its lock. Not all keys will open all locks. The configuration of the two factors must be appropriate. Decidedly forceful and unquestionably unique is the description of the distinctive peculiarity of enzymes lately published by the London physiologist, Professor Halliburton,1 in a primer intended for the general reader. “We may roughly compare an enzyme,” he writes, “to an ill-disposed person who comes into a room full of good-natured people, and who succeeds in setting them all by the ears. He has produced a change in them without undergoing any change himself, by his mere presence. He is, moreover, able to repeat the process over and over again in fresh roomfuls ad infinitum.” Perhaps the expression “enzyme” will now acquire a wider usefulness as a descriptive term for a not entirely unknown type of human being.