604 NERVOUS SYSTEM 



is dead. There seems to be no such thing as death, except as the various 

 tissues and organs which go to make up the entire body become so 

 altered as to lose their physiological properties beyond the possibility 

 of restoration ; and this does not occur for all parts of the organism in 

 an instant. A person drowned may be to all appearances dead, and 

 certainly would die without measures for restoration ; yet in such in- 

 stances, restoration may be accomplished, the period of apparent death 

 being simply a blank, so far as the recollection of the individual is 

 concerned. It is as impossible to determine the exact instant when 

 the vital principle, or whatever it may be called, leaves the body in 

 death, as to indicate the time when the organism becomes a living 

 being. Death is nothing more than a permanent destruction of so-called 

 vital physiological properties ; and this occurs successively and at differ- 

 ent times for different tissues and organs. 



When it is seen that frogs will live for weeks, and sometimes for 

 months, after destruction of the bulb, and that in mammals, by keep- 

 ing up artificial respiration, many of the most important physiological 

 acts, such as the movements of the heart, may be prolonged for hours 

 after decapitation, one can understand the physiological absurdity of 

 the proposition that there is any such thing as a vital point, either in 

 the bulb or in any other part of the nervous system. 



ROLLING AND TURNING MOVEMENTS FOLLOWING INJURY OF CERTAIN 

 PARTS OF THE ENCEPHALON (FORCED MOVEMENTS) 



The remarkable movements of rolling and turning, produced by 

 section or injury of certain of the commissural fibres of the encephalon, 

 are not very important in their bearing on the uses of the brain, and they 

 are rather to be classed among the curiosities of experimental physiology. 

 The movements follow unilateral lesions and are dependent, to a certain 

 extent, on a consequent inequality in the power of the muscles on one 

 side, without actual paralysis. These have been called forced move- 

 ments. Injury to the following parts usually determines movements of 

 rotation : 



" i. Cerebral hemispheres; 



" 2. Corpora striata ; 



" 3. Optic thalami (Flourens, Longet, Schiff); 



"4. Cerebral peduncles (Longet); 



"5. Pons Varolii; 



"6. Tubercula quadrigemina, or bigemina (Flourens); 



" 7. Peduncles of the cerebellum, especially the middle, and the 

 lateral portions of the cerebellum (Magendie); 



