CHAP, ii.] THE BRAIN. 765 



tion supports this view. On the one hand in certain cases (and 

 the number of these is increasing) it has been possible to ap- 

 ply an electric current to the human brain laid bare or covered 

 only with the membranes; the results obtained distinctly cor- 

 roborate the above view. We may note in passing that in such 

 cases it has been found necessary to apply a relatively strong 

 current. On the other hand corroboration is also afforded by 

 cases of disease, by the phenomena attending circumscribed affec- 

 tions of the cortex, such as tumours and the like, and that in 

 spite of the advantages of dealing with one of ourselves being 

 counterbalanced by the disadvantages due to disease being so 

 often anatomically diffuse and physiologically changeful and 

 progressive. 



We said above that during experiments on animals stimu- 

 lation of any part of the motor region may under abnormal 

 conditions lead to general epileptifonn convulsions. Mow clin- 

 ical study has shewn that in man certain kinds of epileptic 

 Attacks are of similar cortical origin. In these cases it has been 

 observed that the attack begins in a particular movement, by 

 contractions of particular muscles, or of the muscles of a par- 

 ticular region of the body, of the hand, foot, toe, thumb, &c., 

 and then spreads in a definite order or 'march' over the mus- 

 cles of other regions until the whole body is involved. When 

 in an experiment on an animal epileptiform convulsions super- 

 vene, they similarly start from the region of the body, the 

 motor area of which is beneath the electrodes at the time, and 

 similarly spread by a definite ' march ' over the whole body. 

 Hence in the human epileptiform attacks of which we are 

 speaking, it has been inferred that the immediate exciting cause 

 of the attack is to be sought in events taking place in that part 

 of the cortex which serves as the area for the movement which 

 ushers in the attack. Further inquiry has not only confirmed 

 this view, but has also shewn that the topography of the corti- 

 cal areas in man, as thus determined, very closely follows that 

 of the monkey. 



Other diseases of the cortex have been marked, among other 

 symptoms, by loss or impairment of particular movements. In 

 most of such cases, the cortical lesion has been of such an 

 extent as to involve a number of special areas at the same time, 

 and so to lead to loss or impairment of movement over relatively 

 considerable regions of the body, such as the whole of one arm ; 

 and in general the teaching of these cases of disease, while con- 

 firming the deductions from the monkey, and giving us some 

 general idea of the topography of the human motor cortical 

 region, has at present given us approximate results only. Figs. 

 136 and 137 shew in broad diagrammatic manner the position 

 and relative extent of the motor areas for the leg, arm and face 

 in man, so far as has yet been ascertained. To assist the reader 



