244 THE BIOPHYSICAL PROBLEM OF NERVE CONDUCTION 



like state altered the encephalogram in the same general way as natural 

 sleep. The more nearly alike the clinical actions of two drugs are, the 

 more nearly alike are the changes which they produce in the record. 



An encephalogram obtained during epileptic seizures shows distinct 

 and characteristic potential waves. It was found that the rhythm which 



Grand Mai Seizure _ 



High-voltage fast waves + I50/*V 



Ton 1 - Clonic 



Petit Mai Seizure 

 Fast wave and spike ~l2007tv 



Petit Mai Variant 

 Slow wave and spike 



+ l50/iv 



12 3 4 5 6 7 Seconds 



Fig. VI-19. Types of abnormal activity encountered in epilepsy and the variety 

 of seizure with which each is associated. Grand mal seizure: typical pattern, elec- 

 trodes on left frontal region and ear. Petit mal seizure: left frontal region and ear. 

 Petit mal variant: left occipital region and ear. (By courtesy of F. A. Gibbs, E. L. 

 Gibbs, and W. G. Lennox [1939].) 



is developed during seizures is distinctive for the three main types of 

 epilepsy. Figure VI-19 shows the fast rhythm of " grand mal " and the 

 alternating fast and slow rhythm of " petit mal." The exact pattern 

 tends to be characteristic for each patient. 



The well-established facts are that the presence or the absence of the 

 a rhythm is not correlated with intelligence and that different individu- 

 als differ widely from one another in general wave pattern, yet a given 

 individual tends to reproduce his own record on successive tests. The 

 a rhythm content varies under different circumstances. The onset of 

 drowsiness, any startling stimulus, or conditions of embarrassment and 

 apprehension may inhibit it. Overactivity of a pathological sort illus- 



