Temperature of the Brain in relation to Psychical Activity. 83 



March 24, .1892. 



Mr. JOHN EVANS, D.C.L., LL.D., Treasurer and Vice-President, 



in the Chair. 



The Right Hon. Spencer Compton Cavendish, Duke of Devonshire, 

 was admitted into the Society. 



A List of the Presents received was laid on the table, and thanks 

 ordered for them. 



The Croonian Lecture was delivered as follows : — 



Croonian Lecture. — "The Temperature of the Brain, especi- 

 ally in relation to Psychical Activity." By Angelo MOSSO, 

 Professor of Physiology in the University of Turin. Re- 

 ceived March 24, 1892. 



(Abstract.) 



In his investigations on the temperature of the brain the author has 

 employed, in preference to the thermo-electric pile, exceedingly sen- 

 sitive mercurial thermometers, constructed specially for the purpose. 

 Since each thermometer contains only 4 grams of mercury, the 

 instruments respond very rapidly to changes of temperature, and a 

 change of not more than 0002° C. can easily be measured by means 

 of them. The author has studied the temperature of the brain, com- 

 paring it with that of arterial blood, of the muscles, of the rectum, 

 and of the uterus ; his observations were made on animals under 

 the influence of morphia or various anaesthetics, and also on man. 



The curves of the observations made show that in profound sleep a 

 noise, or other sensory stimulus, is sufficient to produce a slight 

 development of heat in the brain, without the animal necessarily 

 awakening. 



In profound sleep the temperature of the brain may fall below that 

 of the blood in the arteries. This is due to the very great radiation 

 of heat which takes place from the surface of the head. 



The brain when subjected to the action of the ordinary interrupted 

 current rises in temperature. The rise is observed earlier in the 

 brain than in the blood, and the increase is greater in the brain than 

 in the general blood-current or in the rectum. During an epileptic 

 seizure brought on by electrical stimulation of the cerebral cortex, 



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