CEREBRAL LOCALIZATION 677 



This conception is correct, because it has subsequently been shown 

 that the stimulus arises in the gray matter of the cerebral cortex and 

 not in the fibers leading away from this area. This is proved by the 

 fact that the latent period, i.e., the time elapsing between the moment 

 of the appHcation of the stimulus and the beginning of the muscular 

 movement, is longer when the stimulus is applied to the surface of the 

 gray matter than when brought to bear directly upon the underlying 

 white matter. This result clearly betrays the controlling influence of 

 the cells composing this area. Central formative processes always 

 consume a much longer time than the mere passage of the impulses 

 over nerve-tissue. In addition, it has been proved that the gray matter 

 possesses a lower threshold value of stimulation than the white matter. 

 In other words, a lesser strength of current is required for its activation 

 than for that of the underlying fiber substance. This relationship, 

 however, may be reversed by painting the cerebral surface with cocain 

 or chloral.^ 



In this connection it should be stated that muscular movements 

 may also be evoked by the stimulation of very restricted areas of the 

 occipital and temporal lobes. These movements, however, remain 

 confined to the extrinsic muscles of the eyes and ears and seem, there- 

 fore, to be the direct outcome of the psychic processes occurring in 

 these particular areas. The impulses here generated are transferred 

 first of all to the motor area in the precentral convolution and later 

 on to the distant motor organs. Hence, neither the occipital nor the 

 temporal lobes should be regarded as true motor centers, although 

 both are in a position by means of close association paths to activate 

 the chief motor center in the anterior central region. 



Traumatic Epilepsy. — It has previously been stated that the 

 muscular spasms associated with epileptic seizures, have been attributed 

 by Jackson^ (1864) to a mechanical irritation of a particular area of 

 the cerebral cortex. This assertion, which was made sometime before 

 the publication of the work of Fritsch and Hitzig, was based upon the 

 fact that certain types of epileptics present definite lesions of the cere- 

 bral gray matter. A few years later it found confirmation in the ob- 

 servation of Fritsch and Hitzig proving that the application of a strong 

 galvanic current to the surface of the motor region gives rise to 

 powerful and lasting muscular contractions. Ferrier, Luciani and 

 Unverricht^ showed subsequently that these seizures need not remain 

 localized, but may acquire a progressive character until they involve 

 the musculature of practically the entire body. So generalized, they 

 constitute the clinical picture which is commonly seen during the con- 

 vulsive seizures of epileptics. It is true, however, that an increase 

 in the strength of the current is not the only means by which these 



1 Francois — Frank and Pitres, Arch, de Physiol, norm. et. path., 1883. 



2 Hitzig, H. Jackson und die motor. Rindenzentren im Lichte der physiol. 

 Forschung, Berlin, 1901; also: H. Jackson, A Study of Convulsions, London, 1870. 



^ Archiv fiir Psychiatric, xiv, 1880, 175. 



