OH. XLVIII.] FUNCTIONS OF THE CEREBRUM. 667 



CHAPTER XLVIII. 



FUNCTIONS OF THE CEREBRUM. 



THE brain is the seat of those psychical or mental processes which 

 are called volition and feeling ; volition is the starting point in 

 motor activity ; feeling is the final phase of sensory impressions. 



In the days of the ancients very curious ideas prevailed as to 

 the use of the brain. It is true that Alkmaon as early as 580 B.C. 

 placed the seat of consciousness in the brain, but this view was 

 of the nature of a guess, and did not meet with general accept- 

 ance ; and two hundred years later Aristotle considered that the 

 principal use of the brain was to cool the hot vapours rising from 

 the heart. At this time the seat of mental processes, especially 

 those of an emotional kind, was supposed to be in the heart, an 

 idea now confined to poets, or in the bowels, as those acquainted 

 with such ancient writings as the Bible will know. 



As time went on truer notions regarding the brain came to the 

 fore ; thus Herophilus (300 B.C.) was aware of the danger attend- 

 ing injury to the medulla; Aretaeus and Cassius (97 A.D.) knew 

 that injury to one side of the brain produced paralysis of the 

 opposite side of the body; and Galen (131 203 A.D.) was acquainted 

 with the main motor and sensory tracts in brain and cord. Be- 

 tween that time and this, most of the celebrated anatomists have 

 contributed something to our knowledge, and one may particularly 

 mention Vesalius, Sylvius, Rolando, Gall, Carus, Willis, and 

 Burdach ; many of these names are familiar because certain 

 structures in the brain to which they called attention have been 

 christened after them. The erroneous notion that the brain was 

 not excitable by stimuli lasted even to the days of Flourens and 

 Magendie. In modern times, new methods of research in the 

 microscopic and experimental direction have produced results 

 which perhaps in no other branch of physiology have been of 

 such immediate benefit to the human race. 



Effects of Removal of the Cerebrum. 



When the cerebral hemispheres are removed in a frog, it is de- 

 prived of volition and of feeling ; it remains perfectly quiescent 

 unless stimulated ; it is entirely devoid of initiatory power, but 

 as we have already seen, it will execute reflex actions many of 

 which are of a complex nature (see p. 660). 



