ON THE FUNCTIONS OF THE BRAIN. 7 i 



secretes, production of heat invariably takes place at the same time 

 with increased activity in the phenomena of local circulation. 



Is the case the same with the nervous system and the brain? 

 Modern experiments forbid us to doubt it. Whenever the spinal 

 marrow and the nerves exhibit sensibility or movement, whenever an 

 intellectual effort takes place in the brain, a corresponding quantity 

 of heat is evolved in it. We must, then, regard heat in the animal 

 economy as a resultant of the organic labor of all the parts of the 

 body ; but at the same time it becomes also the principle of activity 

 for each of these parts. This correlation is, above all, indispensable for 

 the brain and the nervous system, which hold all the other vital actions 

 under their control. Experiments have demonstrated that the tissue 

 of the brain exhibits a higher temperature than any other organ of the 

 body. In man and the warm-blooded animals the brain itself produces 

 the heat required for the manifestation of the peculiarities of its tissue. 

 If this were not so, it would infallibly grow cooler, and we should at 

 once see all the functions of the brain become torpid, and intelligence 

 and will perish. This does, in fact, occur in cold-blooded animals, in 

 which the function of heat-production is not energetic enough to sus- 

 tain the organism in resistance to external causes of refrigeration. 



III. 



With respect to the organic or physico-chemical conditions of its 

 activity, the brain, then, presents nothing exceptional. If we *:rn to 

 experiments made upon it by physiologists, we shall find that they 

 have succeeded in analyzing cerebral phenomena in the same way as 

 those of all the other organs. The experimental process usually em- 

 ployed to determine the functions of organs consists in removing them 

 or in destroying them either gradually or suddenly, so as to determine 

 the uses of the organ according to the special disturbances thus caused 

 in vital phenomena. This method of the removal or destruction of 

 organs, which forms a sort of brutal vivisection, has been applied on 

 a great scale to the study of the whole nervous system. Thus, aftei a 

 nerve is cut, when the parts to which it had been distributed lose their 

 sensibility, we conclude from this that it is one of the nerves of sensa- 

 tion ; if it is motion that ceases, we infer thence that we are dealing 

 with one of the nerves of motion. The same method has been applied 

 in examining the functions of the different parts of the encephalic organ, 

 and, though the complexity of the parts has occasioned novel difficulties 

 of execution, the method has yielded results that are not to be con- 

 tested. Every one has long known that, without the brain, intelligence 

 is not possible, but experiment has discovered exactly the part that 

 is played by each portion of the organ. It teaches us that conscious- 

 ness, or intelligence properly so called, resides in the cerebral lobes, 

 while the lower portions of the brain contain nervous centres destined 



