THE BRAIN. 535 
There is a kind of experimental evidence that throws a good 
deal of light on the present discussion. It is found that, when 
certain drugs have been administered, the irritability of the 
cortex is either increased or diminished, according to the stage 
of action of the drug (morphia, etc.). It is not impossible 
that epileptiform convulsions may result from the application 
of a stimulus of almost any strength, though this result does 
not follow when the electrodes are applied to the underlying 
white substance. The disease epilepsy has been known to fol- 
low injuries to the cranium or the brain membranes, in conse- 
quence of which. the cells themselves of the cortex have been 
altered in function. Moreover, the epileptiform movements 
may be in such cases confined to certain muscles, thus pointing 
to a motor localization. If a muscle contraction, as the result 
of stimulation of a motor area (the animal being under the in- 
fluence of morphia), be recorded by the graphic method, and the 
sciatic nerve then divided, in repeating the original experiment, 
it will be seen that the whole character of the curve is altered, 
the latent period having been lengthened, and the height of 
the curve lessened. This points to an inhibitory influence exer- 
cised over the cortical motor cells, by afferent influences, and we 
are at once reminded of Schiff’s theory ; but most of all do such 
experiments enforce that close relationship of all parts of the 
body which finds its reflection in the brain cortex as elsewhere. 
We have dwelt upon the subject of cerebral localization at 
length, because of its great practical and scientific importance, 
not alone for medicine and physiology, but in the allied depart- 
ment of psychology. In conclusion, we may express the view 
that there is in the cerebral cortex a localization of function, 
variable for each group of animals, and to some extent for 
each individual ; that it is not of a character to be mapped out 
by mathematical lines; that in case of disease or injury one 
part may to a certain extent take up the functions of another ; 
that the functions of any part, however limited, are only to be 
understood when taken in connection with all other parts of - 
the cortex, of the brain, and, in fact, of the entire body. These 
views we believe to be borne out by the facts of physiological 
experiment, clinical medicine, operative surgery, pathology, 
sleep, dreaming, hypnotism, the nature of the cerebral circu- 
lation, and the general truths of biology. 
Cerebral Time.—We have already considered cerebral reflex 
time, and now proceed to examine into the period occupied by 
a mental operation involving attention and volition. 
