?06 PHYSIOLOGY, 



charge was suddenly exploded, driving the bar so that it entered the 

 man's lower jaw and came out at the top of the head close to the 

 sagittal suture in the frontal region. It fell at some distance, covered 

 with blood and brains. For the moment the victim remained uncon- 

 scious. An hour after the accident he walked to the house of a sur- 

 geon, where he gave an intelligent account of the accident. For a 

 long time his life was despaired of, but he finally recovered to live 

 twelve and one-half years longer. 



It may be concluded, therefore, that one cerebral hemisphere only 

 is sufficient for the mobility and sensibility of the two sides of the 

 body, as well as the performance of psychical functions. The indi- 

 vidual with one hemisphere destroyed remains like one who has lost an 

 eye. That is to say, the brain continues to perform its functions, ani- 

 mal as well as psychical, but with noticeable weakness^ greater effort, 

 and fatigue. The frontal lobes are the chief seat of the will, of the 

 memory, and intellectual functions. 



The irritability of the cerebral cortex may be diminished or ex- 

 aggerated by various circumstances. Thus, opium, ether, chloroform, 

 chloral, the bromides, cold, asphyxia, etc., diminish it. Inflamma- 

 tion, urea, uric acid, atropine, strychnine, etc., increase its excita- 

 bility. 



Action of Brain Extracts. In 1898 I found that infusions of 

 dried brain reduced the heart's frequency and the arterial tension. 

 Section of the vagus or its paralysis by atropine did not prevent this 

 action. Halliburton did not obtain the same results after the use of 

 atropine, but my experiments have been confirmed by Swale Vincent 

 and Sheen. Quite recently Swale Vincent and Cramer have found two 

 substances in brain, both depressing the heart even after the previous 

 use of atropine. They also obtained another substance depressing the 

 circulation, but its effects are abolished by atropine. 



SLEEP. 



Sleep is characterized by a suspension of consciousness, a dim- 

 inution of reflex activity of the nerve-centers, a decrease of the 

 excitability of the nerves, and a lessening in all the chief functions 

 of the body. The activity of the cerebral motor centers is nearly sus- 

 pended in the majority of animals as they seek a reclining position. 



In extreme fatigue sleep is preceded by yawns, a want of atten- 

 tion, a decrease of sensibilit}^ in the special senses, a progressive loss 

 of movement, and a dropping of the upper eyelids. The eyes are 

 closed, vision is necessarily then abolished. The pupil is contracted, 



