236 HUMAN PHYSIOLOGY CHAP. 



the mind is active more blood goes to the brain, oxida- 

 tion is increased, the temperature rises, and the brain 

 cells become fatigued. When the brain is seriously 

 injured or diseased, the mind does not work as it 

 should ; the person behaves in a strange way. He can- 

 not remember, imagine, and reason as he once could ; 

 his feeling and will power are lost or enfeebled ; his 

 whole mind, with all its powers and capacities, hopes 

 and ambitions, has become so deranged that he cannot 

 be held responsible for what he does, and we call him 

 mad or insane. 



Sometimes a person suddenly loses the ability to 

 speak. A judge of the Supreme Court in one of our 

 states, after spending an evening in pleasant conversa- 

 tion with some friends at his house, retired at his usual 

 time, apparently in the best of health. The next morn- 

 ing he could not utter a single sentence. The power 

 of speech was gone. He was as helpless as if he had 

 never learned to talk. After a vacation of several 

 months he recovered fully. Cases of this kind are 

 known to physicians, for they are not uncommon. The 

 loss of speech is sometimes due to the formation of a 

 blood clot over the speech area of the brain caused by 

 the rupture of small blood vessels. In such cases the 

 skull has been opened and the hard clot carefully re- 

 moved without injuring the delicate brain tissue, and 

 the ability to speak was regained in the course of a few 

 weeks. When no operation is performed, the clot may 

 in time be completely absorbed so that the patient re- 

 covers. 



