7 o THE POPULAR SCIENCE MONTHLY 



Facts analogous to those observed in animals have been studied 

 directly in the human brain. Upon a person injured by a frightful 

 railroad accident the effect of a considerable loss of brain-substance 

 was examined. The brain was visible over a surface of three by six inch- 

 es. The patient suffered frequent and severe attacks of epilepsy and 

 coma, during which the brain invariably expanded. Sleep succeeded 

 these attacks, and the cerebral hernia gradually subsided. When the 

 patient awoke, the brain again projected and rose to the level of the 

 surface of the external, bony table. In the case of another person in- 

 jured in consequence of a fracture of the skull, the cerebral circulation 

 was studied during the administration of anaesthetics. With the first 

 inhalations, the surface of the brain became branchy and filled with 

 blood ; the flow of blood and throbbing of the brain increased, and 

 then, at the instant of sleep, its surface subsided by degrees below the 

 opening, while at the same time growing relatively pale and blood- 

 less. 



Briefly, then, the brain is governed by the common law that con- 

 trols blood-circulation in all the organs. By virtue of this law, when 

 the organs are at rest and their action suspended, the circulation in 

 them grows languid ; and it increases, on the contrary, as soon as activ- 

 ity is resumed. The brain, I repeat, is no exception to this general law, 

 as had been supposed, for it is now demonstrated that the state of 

 sleep coincides not with congestion, but, on the contrary, with blood- 

 lessness of the brain. 



If we seek now to understand the relations that may exist between 

 great activity of blood-circulation and the functional condition of the 

 organs, we shall readily see that this increased flow of the sanguineous 

 fluid corresponds with greater intensity in the chemical alterations 

 going on within the tissues, as also with an exaltation in the phenomena 

 connected with heat which are their necessary and immediate conse- 

 quence. The production of heat in living beings is a fact established 

 from remote antiquity ; but the ancients had erroneous ideas as to the 

 origin of heat : they attributed it to an innate organic power that had 

 its seat in the heart, that ardent centre of ebullition for the blood 

 and the passions. At a later date the lungs were regarded as a sort 

 of furnace to which the mass of the blood repaired successively to gain 

 the heat which circulation was bidden to distribute throughout the 

 body. The advance of modern physiology has proved that all these 

 absolute consignments of vital conditions to special jx>ints are chimeras. 

 The sources of animal warmth exist everywhere, and in no region 

 exclusively. It is only through the harmonious functional play of the 

 various organs that the temperature is kept nearly constant in man 

 and the warm-blooded animals. There are, in truth, as many heat-pro- 

 ducing centres as there are special organs and tissues, and we are 

 obliged always to connect evolving heat with functional labor of the 

 organs. When a iruscle contracts, when a mucous surface or a gland 



