The Human Conducting-system and Its Examination.

It may be said that the survival of the race depends upon the reproductive organs but that the survival of the individual to three score and ten depends, as much as anything, upon the integrity of the conducting system of the heart, namely, the sinu-atrial pacemaker of Keith and Flack (1906 and 1907), and Lewis (1910-11), and the atrioventricular node with its bundle and branches, known as the His-Tawara system. The writings of these giants of research have provided most of our present anatomical knowledge of this specialized neuromyocardial system which initiates and conducts the impulse for cardiac contraction. This knowledge has been available since the beginning of this century, but the advent of intracardiac surgery has brought the subject into the limelight once more for a new generation to study. I can add nothing important to this knowledge; the object of this communication is to present a simple routine for examining the system which any pathologist can apply successfully when faced with the task. Hitherto, the matter has been somewhat shrouded in the obscurity created by the specialistas in so many other fields. It is no use pretending that the interpretation of histological appearances is easy but a good series of sections at least will allow an exchange of views. The results to be expected are exactly proportional to the care with which the examination is carried out. Hit-or-miss methods are