680 FUNCTIONS OP THE CEREBRUM [cK. XLVIII. 



a theory, it is an accepted fact. Perhaps the best practical evidence 

 of this is the fact that experiments 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 Terrier and Yeo, 

 and later by Schiifer, 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 com- 

 pared the position of the disease with the symptoms exhibited by the 

 patients during life. In this way two series of independent investi- 

 gations have led to the same results ; both methods are essential, as 

 many minor details discovered 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 orna- 

 mental finish to the brain. The idea that the basal ganglia were so 

 important 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. 655). 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 movement, and 

 the optic thalamus, in connection with sensation, and especially with 

 the sense of vision as its name indicates. 



A subsidiary centre may be compared to a subordinate official in 



