BRAIN AND NERVOUS SYSTEM. 343 



787. Liicbig says that action of the brain implies change of 

 particles and waste, and, therefore, a greater supply of blood. 

 To meet this increased want, the arteries beat with greater 

 force, and send more blood, whenever the mind and the 

 'brain are excited or active. Sir Astley Cooper saw this in 

 a young man who had lost a portion of the skull. " His 

 brain could be distinctly seen beating, through the opening 

 of the skull ; " and, whenever he was irritated by any oppo- 

 sition, the pulsation was much more violent, and it became 

 more quiet when he was calm, and his mind was easy.* 

 There was a girl in Montpellier, France, who had lost a large 

 portion of the scalp and skull. Her brain could be seen for 

 a considerable extent of surface. "When she was in a 

 dreamless sleep, her brain was motionless, and low within 

 the cranium; but when her sleep was imperfect, and .she was 

 agitated with dreams, her brain moved" and beat, more 

 blood was sent to it, the arteries expanded, and the brain 

 protruded through the hole in the bone. This protrusion 

 was greater in active than in calm dreams ; and when she 

 was awake, the same difference was observed, consequent 

 upon the activity and the quiescence of her mind. If she 

 was in vigorous thought, the brain swelled, and protrusion 

 was very observable.t 



788. The eye becomes weary with long exposure to 

 light, and seeks rest and relief in shade ; and, if not thus 

 relieved, it- finds it difficult to discriminate objects. The 

 muscles, also, are fatigued with long and continuous exer- 

 tion, and are incapable of contraction. Rest restores this 

 power. So the brain is fatigued with long and uninterrupted 

 attention to subjects of deep thought, and incapable of fix- 

 ing its attention upon matters of a grave nature ; then it 

 wants, and must have, opportunity of rest to recover its 

 energies ; and, if this is not granted, the brain and the 

 mind will be weakened or disordered. 



789. Sleep is the^natural rest of the brain. It gives rest 

 to the mind and to the voluntary organs of the body. The 



* Surgical Lectures. 



f Combe, 255. Annals of Phrenology, No. I. p. 39. 



