450 BIOLOGY. [Book vii. 



salivary glands, the venous blood issuing from the gland grows 

 always warm when this gland is in a state of activity.^ 



The observations thus made upon the sanguineous glandular 

 vessels have besides brought into prominence one of the most 

 interesting physiological phenomena, namely, that if the oxyda- 

 tion of the living tissues and substances is the principal cause of 

 organic heat, it is not the only one. In effect the glandular 

 venous blood, which is black and oxydised during the repose of 

 the glands, becomes, on the contrary, rutilant when the gland 

 becomes again active, and at the same time its tempei'ature 

 rises. It is then less burned, contains more oxygen, and less 

 carbonic acid. The venous blood of glands with intermittent 

 functionment, like the salivary glands, thus passes alternately 

 fi'om black to red, according as the glands are in a state of 

 repose or in movement. On the contrary, the venous blood of 

 glands perpetually active, like the kidney, is always warm 

 and vermilion. Slow oxydation, organic combustion, is here 

 only a secondary agent of temperature, of which the principal 

 causes are the isomerias, the catalyses, the evolvements taking 

 place in the substance of the glandular organs.^ 



In all the other organs it is oxidation which prevails; the 

 efferent or venous blood is always black, and it is the blacker, 

 the more burned in proportion as the organ has functionated 

 with greater activity. Thus the brain, so rich in capillary 

 vessels, has normally a very high temperature. Professor Schiff 

 has proved directly that the temperature of the cerebral hemi- 

 spheres rises when they functionate ; we know also that these 

 organs are the seat of a kind of vascular erection, of active 

 congestion, while, on the contrary, during dreamless sleep the 

 brain is pale and ansemic. Observations made upon trepanned 

 animals, and also upon man, in cases of loss of substance of the 

 bones of the skull, have put these interesting facts beyond 



1 CI. Bernard, Chaleur Animale, in Eemie Sciervtifique, 1872, TSo. 45. 

 ^ CI. Bernard, loo. cit.. No. 47. 



