THE FUNCTIONS OP THE CEREBRUM. 271 



graded electric stimulus, say, the center of the thumb, it will 

 be found that the thumb undergoes a slow, purposeful, co-ordi- 

 nated movement; and so on for every other center. Or, if in- 

 stead of stimulating, we cut away one of the centers and allow 

 the animal to recover from the immediate effects of the opera- 

 tion, it will be found that all the more finely co-ordinated move- 

 ments of the corresponding part of the body have disappeared, 

 although gross reflex movements may be possible, because the 

 spinal reflexes are still intact. If the entire Rolandic area on 

 one side is removed, the muscles of the opposite side of the bod3 r y 

 except those of the trunk, become completely paralyzed for 

 some time, after which, however, particularly in the case of 

 young animals, the paralysis becomes recovered from, thus in- 

 dicating that some other portions of the brain have assumed 

 the function of the destroyed centers. If the stimulus is a very 

 strong one, the movements do not remain confined to the cor- 

 responding muscle group, but they spread on to neighboring 

 groups until ultimately the whole extremity or perhaps even 

 all the muscles of that side of the body are involved. 



These experimental results find their exact counterpart in 

 clinical experience. Thus when some center becomes irritated 

 by pressure on it of some tumor growing in the membranes of 

 the brain (meningeal tumor), or by a piece of bone, as in de- 

 pressed fracture of the skull, or by blood clot, convulsive at- 

 tacks (known as Jacksonian epilepsy) become common. The 

 first sign of such an attack is usually some peculiar sensation 

 (aura) affecting the part of the body which corresponds to the 

 irritated area, then the muscles of this part begin to twitch and 

 more muscles get involved until ultimately all those of the cor- 

 responding half of the body become contracted. There is, how- 

 ever, no loss of consciousness, which there is in true epilepsy. 

 The evident cause of these symptoms has clearly indicated the 

 proper treatment for such cases, namely, surgical removal of 

 the cause of irritation. For this purpose a very careful study 

 is first of all made of the exact group of muscles in which the 

 convulsions originate, the location of the area on the cerebrum 

 is thus ascertained and a trephine hole is made in the correspond- 



