THE SCOPE OF MINI). 243 



'"iiiLMlulla" or lower brain, each of these contaiiiinii^- a large 

 pr()])ortion of the active ag'eiit in brain Avork known as grey 

 matter, which consists of masses of brain cells. 



The mednlla or lower brain connects the spinal cord 

 l)elow with the mid-brain above, and is " the co-ordinating 

 centre of most associated movements."* It is in fact the 

 organising centre for carrying on all the processes connected 

 with the passive or vegetative life of the bod}- as contrasted 

 with the active or animal life. All the processes carried on 

 here are far below the level of conscionsness. 



The basal ganglia of the mid-brain are principally three 

 in number ; the corpora quadrigemina, connected with sight, 

 the corpora striata with motion, and the optic thalami witli 

 sensation. 



In this mid-brain we see the organization of the functions 

 of animal life subject to, or of an inferior order to, the highest 

 centres and conducted without consciousness. 



Lastly, we come to the cortex or surface brain, the seat 

 of conscious mental life and the source of all voluntary 

 actions. 



The cortex is the seat of conscious sensation, though we 

 are by no means conscious of all that takes place even in the 

 cortex, for innumerable sensations may, and probably do, 

 continually reach it of which we are Avholly or partially 

 unconscious ; in many cases, of course, this is accounted for 

 by non-attention. On the other hand, it would appear from 

 recent researches that it is not possible to be conscious of any 

 currents that do not reach the surface of the brain. 



With regard to there being two hemispheres right and 

 left, Gall, Spurzheim, Dr. A. L. Wigan, Sir H. Holland, 

 and Brown Sequard conclude we have two brains united for 

 common action, and that we have probably two minds acting- 

 normally in perfect harmony, but which can and do act 

 separately in many conditions. 



When a nerve cell acts (whatever this means}, impulses 

 tend to pass off from it along its various connected nerve 

 fibres, and the force and number of these impulses depend on 

 the violence of the cell action ; if this is gentle there may 

 be only a slight impulse passing off through the largest con- 

 necting fibre (the freest channel); if the action is violent it 

 may overflow through the various connecting fibres in any 

 direction. 



* Feriier, Functions of the Brain. 



II 2 



