It is my intent in this paper briefly to call attention to a type of observation which has come to be commonplace to the pharmacologist but which is perhaps not brought so forcefully to the attention of those whose interest is therapeutics rather than pharmacology. This is the matter of the variability in response to drugs. I do not mean to infer that the physician does not recognize that patients do vary in this respect. Indeed, one of the factors in the successful treatment of disease is the physician's ability to recognize and to correct for such deviations from expected behavior. It is to be emphasized, however, that variability — individual variation—is not a perverse disturbance but is rather the condition to be anticipated. It represents, in fact, the normal — the expected situation — if the observations of the pharmacologist in the laboratory have any validity.
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