. Geology and Natural History. 241 
devoted to particular manifestations is a subject on which we have 
only imperfect speculations or data too insufficient for the forma- 
tion of a scientific opinion. The general view is that the brain as 
a whole subserves mental operations, and that there are no parts 
his has_ been 
seem to agree with this doctrine. One of these is that when a 
certain part of the brain is diseased, in Aphasia, the individual is 
in w ther curious phenomena 
have been well described by Dr. Hu hlings Jackson, viz: that 
orm convulsions of the whole of one side, or of the arm or leg or 
the muscles of the face ; and from studying the way in which these 
convulsions show themselves he was able to localise very accurately, 
the seat of the lesion. 
The great difficulty in the study of the function of the brain has 
been in the want of a proper method. When we study the func- 
ion of a nerve, we make our experiments in two ways. In the 
place, we cut the nerve, and observe what is lost. In regard to 
the brain and nervous system, the method has been almost entirely, 
until recently, the method of section. It has been stated by phy- 
Slologists, that it is impossible to excite the brain into action by 
oy. 
About three years ago, two German physiologists, Ft ritsch and 
the brains 
the extent that the might have done, and perhaps 2 not site 
to depend upon irritation of parts of the brain. "ec 
Nnitate the effects of disease on the lower animals, and determined 
‘0 adopt the plan of stimulating the g , ral 
“ity, after the manner described by Fritsch and Hitzig. 
