AN ENQUIRY INTO THE FORMATION OF HABIT IN MAN. 137 



of tlie spirit of man ; the lower, of tlie necessary vital func- 

 tions that cany on and store life's forces — the vegetative side 

 of our life, or hody ; while the middle region is that of the 

 functions of animal life, or what is sometimes called the soul. 

 The actions connected with the cortex are voluntary, those 

 connected with the medulla are involuntary or reflex, while 

 those between the two partake of both varieties of action, 

 being at first largely voluntary in character, but becoming 

 more and more automatic in reflex as habits are formed. 

 The diff'erence of these four divisions of the brain is Ave 11 

 shown in drunkenness. The upper region is afl^ected first, 

 and noisy manifestations of animal life are displayed unruled 

 by the spirit. If the man be drunk, the middle region and the 

 cerebellum are paralyzed, and all equilibrium and movements 

 of animal life are lost. If the man is dead drunk, the 

 medulla alone remains active, carrying on the functions of 

 passive bodily life. 



That the hemispheres or upper regions of the brain, and 

 particularly the surface or cortex proper, are the centres for 

 intelligent brain work, is proved by direct experiment, as 

 we shall see when we consider the various actions of the 

 brain. But we may here remark that the frontal region is sup- 

 posed to be specially connected in some way with thoughts 

 and ideas that do not result in bodily activity; the occipital 

 and part of the parietal regions are the centres of sensation 

 or perception, while the intervening portion is the centre for 

 all motor impulses, which can be readil}'' aroused by touch- 

 ing the part with electric stimuli. 



In idiots the frontal region is found to be very deficient, 

 while in intelligent men it is greatly developed. 



Destruction of the sensory area in the cortex appears still 

 to leave the mechanism of sensation (a dog will see, hear, and 

 even feel, in a sense), but the perception is lost (it does not 

 know what it sees, hears, and feels). 



In the middle or motor area, districts have been carefully 

 mapped out in the right and left hemispheres, correspond- 

 ing with movements in various parts on the opposite 

 side of the body ; but it has been specially observed by 

 Foster that the size of these districts does not correspond with 

 the size of the part moved or the number of muscles or 

 nerves it may contain, but to the more or less elaborate and 

 complicated and intelligent use of the part. Thus the district 

 for the arm is enormous compared to tlie leg, that for the 

 thumb large as compared with tlie fingers. Another proof 



