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It is necessary at intervals to revise our standards of the normal in all sciences. This is particularly desirable in electrocardiography, where important advances are made yearly in its application to the diagnosis of cardiac disease. It is very easy for minor changes in the electrocardiogram to loom too largely in the diagnostic picture ; but if the wide limits of normal variation are realized, some of the pitfalls will be avoided.
Chamberlain et al. (Sat,) studied this question.