CH. XLVIII.] CEREBRAL LOCALISATION. 669 



cerebral function is more than a theory, it is an accepted fact. 

 Perhaps the best practical evidence of this is the fact that experi- 

 ments on monkeys have been taken as the basis for surgical 

 operations on the human brain, and with perfect success. 



The earliest to work in the direction of localisation were 

 Hitzig and Fritsch. The subject was then taken up by Ferrier 

 and Yeo, and later by Schafer, Horsley, etc., in this country, and 

 by Munk and many others in Germany. In addition to those 

 who have studied the matter from the experimental standpoint, 

 must also be reckoned the pathologists, who in the post-mortem 

 room have examined the brains of patients dying from cerebral 

 disease, and carefully compared the position of the disease with 

 the symptoms exhibited by the patients during life. In this way 

 two series of independent investigations have led to the same 

 results ; both methods are essential, as many minor details dis 

 covered by the one method correct the erroneous conclusions which 

 are apt to be drawn by those who devote their entire attention to 

 the other. 



The main point which these researches have brought out is the 

 overwhelming importance of the cortex ; it contains the highest 

 cerebral centres. Before Hitzig began his work, the corpus 

 striatum was regarded as the great motor centre, and the optic 

 thalamus as the chief centre of sensation ; very little note was 

 taken of the cortex ; it appears to have been almost regarded as a 

 kind of ornamental finish to the brain. The idea that the basal 

 ganglia were so importau/ arose from the examination of the 

 brains of people who had died from, or at least suffered from, 

 cerebral haemorrhage. 



The most common situation for cerebral haemorrhage, is either 

 in the region of the corpus striatum or optic thalamus ; it was 

 noticed that motor paralysis was the most marked symptom if 

 the corpus striatum was injured, and sensory paralysis if the 

 optic thalamus was injured. The paralysis, however, is due, not to 

 injury of the basal ganglia, but of the neighbouring internal capsule. 

 The internal capsule consists in front of the motor-fibres passing 

 down from the cortex to the cord, and behind of the sensory fibres 

 passing up from cord to the cortex (see p. 645). Hence, if these 

 fibres are ploughed up by the escaping blood, paralysis naturally 

 is the result. If a haemorrhage or injury is so limited as to affect 

 the basal ganglia only, and not the fibres that pass between them, 

 the resulting paralysis is slight or absent. 



The question will next be asked : What, then, is the function 

 of the basal ganglia ? They are what we may term subsidiary 

 centres ; the corpus striatum, principally in connection with 



