Traumatic Extradural Hæmorrhage. Part II

In a recent article in this Journal* an account was given of the historical development and present practical utility of electro-encephalography. Attention was confined to the general cl'nical aspects of the new science since the technical details are difficult to expound without reference to particular cases and actual records obtained with the apparatus. However, in Case II, recorded above, location of the lesion by electro-encephalography proved more accurate than the conventional clinical methods, and led 'to & successful operation. It was thought that this case, being of local as well as surgical interest, might provide a nucleus for a description of the means whereby such location is achieved. Like electro-cardiography, electro-encephalography involves registration of the minute electrical currents produced by active living cells. Examination of these " bio-electric " phenomena gives us the best " inside information " about the course of living processes which we can obtain at present, but there are many technical d fficullies. The first is the small size of the currents. They bear the same sort of relation to those used, say, in an electric flashlight