The value of the study of the excitatory process in the exposed human heart by Barker, Macleod and Alexander1 is unquestioned. Their observations on electrically induced extrasystoles are of special interest. The deflection of Q-R-S in the three leads took direction according to a semblance of an orderly manner, when considered in relation to the many points stimulated. This direction of Q-R-S in the three leads corresponds to that which is frequently observed clinically and which is not readily understood according to the classic explanation. The result is that at present extrasystoles are not accurately localized with regard to their site of origin.
The work of Barker will probably be a forerunner of a proved pattern whereby one will be able to compare the electrocardiogram of extrasystoles from a patient with those from known sources in the human heart, and to make an accurate statement as to their site