x THE FORE-BRAIN 581 



(S) Some poisons, particularly absinthe, produce convulsive 

 attacks similar to those excited by electrical stimulation of the cor- 

 tex, when they are introduced into the circulation. These attacks 

 are also seen in animals in which the brain-stem is completely 

 severed from the brain (Magnan). Injection of a few drops of 

 tincture of absinthe produces inexcitability of the cerebral cortex, 

 with the simultaneous onset of violent epileptic seizures due to 

 the excitation of the bulbo- spinal centres ( Francois -Franck). 

 Apart from these experiments we know from Owsjannikow's 

 work that the bulb contains a centre for common direct or reflex 

 convulsions, a sort of motorium commune (Chap. VII. pp. 411-13). 

 According to Horsley and Schafer epileptiform convulsions can 

 sometimes be observed after strong and protracted stimulation of 

 the spinal cord, when the cord has been separated from the bulb. 



These facts undoubtedly prove that diffuse epileptiform con- 

 vulsions may be evoked by exciting the whole of the bulbo-spinal 

 centres, either with circulating poisons, or by vigorous and 

 diffuse stimulation, independently of the brain or of the excitability 

 of the cerebral motor cortex. It seems, however, illogical to 

 compare these convulsive phenomena with genuine epileptic fits : 

 they have not the clinical characters of epileptic seizures which 

 invariably begin with symptoms of cortical disturbance, i.e. complete 

 loss or disturbance of consciousness, and convulsive spasms limited 

 to one group of muscles. If the epileptogenic excitation spreads 

 to the lower centres before the fit becomes general, this does not 

 destroy the fact that the essential origin of both Jacksonian and 

 idiopathic epilepsy lies in the cerebral cortex. 



IX. The attempt to discover the physiological significance of 

 the so-called "centres" contained in the excitable area of the 

 cortex has produced a long series of works, giving a minute 

 description of the immediate and remote effects of partial or total 

 destruction of this area. 



The majority of the experiments have been made on dogs. 

 If the whole of the excitable zone on one side, e.g. the left hemi- 

 sphere, is excised, the animal as soon as it comes out of the 

 anaesthetic has complete paralysis of the right side. It lies on 

 this side with its four limbs flexed. If the limbs are stretched 

 passively, it only draws the left ones back. It walks with 

 difficulty, turning to the left, to which side its neck and head 

 are also bent, and often falls owing to flexion of its right limbs, 

 which are frequently placed with the dorsum of the foot on the 

 ground. The muscles of the right half of the face, which has the 

 immobility of a mask, are also paretic. It does not react to any 

 abnormal position in which the right limbs may be placed ; 

 sensibility to pain is somewhat blunted, and tactile sensibility 

 seems almost lost on the right side. 



This motor hemiplegia and disturbance of cutaneous and 



