1878.] 



the Temperature of the Head. 



167 



for examining the temperature of the surface of the head, with a view 

 to assisting in the diagnosis and localization of cerebral disease. 



2nd. To see if, from an examination of the relative temperatures of 

 different portions of the surface of the head during increased mental 

 activity, any information could be obtained as to the comparative 

 importance of the parts played by different portions of the brain in 

 the evolution of thought and the different emotions. 



To commence with the first of these ultimate objects of the in- 

 vestigations, it is easy to see that everything depends upon an accurate 

 knowledge of the normal relative temperatures of the different portions 

 of the surface of the head, and the variations of such temperatures 

 within healthy limits. Without this knowledge it is impossible to 

 come to any satisfactory conclusion as to the existence of localized 

 cerebral disorder by examining the temperature of the surface of the 

 head. 



So far as the writer is aware, Dr. Wm. A. Hammond,* of New 

 York, was the first to indicate that a difference of temperature exists 

 between the two sides of the head in health. In 1875, Dr. Hammond, 

 making use of a thermo-electric apparatus, devised by the writer the 

 year previous, came to the conclusion, from observations made on a 

 large number of individuals, that the left side of the head has a higher 

 temperature than the right side. Unfortunately the notes furnished 

 by Dr. Hammond, in the writer's possession, do not state the exact 

 locality examined, a matter of great importance as will be seen 

 further on. 



During the past year M. Brocaf has brought forward experiments on 

 the same subject. M. Broca, using thermometers, has also come to 

 the conclusion that the left side of the head has the higher tempera- 

 ture. The sources of error in M. Broca's method will be presently 

 noticed. 



Turning now to the second of the ultimate objects of the present 

 investigations, namely, the connexion between the relative share of 

 mental work done in a given part of the brain, and the relative tem- 

 perature of the surface over such part, it is evident that here also a 

 thorough acquaintance with the relative temperatures of the different 

 portions of the surface of the head in the quiescent mental condition 

 is requisite. 



As regards what has been already done on the subject of the relation 

 between heat and mental work, it may be summed up in a few words. 



In 1866 the writer commenced a series of experiments with thermo- 

 electric apparatus on the effect of increased mental activity on the 

 temperature of the head. These experiments showed that the exercise 



* Dr. Hammond's paper was read before the New York Neurological Society, 

 October 4, 1875. 



t " Revue Scientifique," September 15, 1877. 



