410 TEMPERATURE AND LIFE. 



combustibles). 'We shall have occasion to refer to this point later on. 

 Calorification is produced not only in the lungs, as Lavoisier believed 

 up to a certain point, but in all the tissues of the organism, the proof 

 of it being that the tissues respire in a condition of life. Exception is 

 made, however, of cutaneous growths, such as hair and nails, these be- 

 ing lifeless portions of the organism. If the tissues respire it is because 

 there is a combination of oxygen and carbon, hence combustion, hence 

 heat. The demonstration of the respiration of the tissues is easily fur- 

 nished by experiment. Let an animal be killed and fragments of mus- 

 cle, liver, brain, bone, etc., detached. Let these be placed in a test 

 tube containing oxygen, and inverted on mercury. At the end of a 

 space of time, which varies in length, and in proportion differing ac- 

 cording to the tissues, there will be found in the test tube carbonic 

 . acid which has replaced a part of the oxygen, and which establishes in 

 an indisputable manner the respiration which has taken place. 



In short, animal heat results from combustion of the carbon in the 

 tissues with the oxygen of the air, this element being introduced into 

 ;the blood by the action of the lungs, and carried by this liquid through- 

 'out every portion of the body. Combustion takes place in all the tis- 

 sues (and in the blood itself, although but slightly) in varying degrees, 

 being greater in extent in the muscles, brain, and glands, and less so 

 in the bones and other anatomical portions of the structure. 



Is calorification, then, the result of combustion and oxydation only? 

 It was for a long time so believed, but in reality other influences enter 

 into this function. The organism is, in fact, the theater of chemical 

 phenomena, infinite in variety. The materials derived from the food 

 are assimilated by various chemical processes, and the action of elimi- 

 nation is accomplished by phenomena of no less variety. All the com- 

 binations, decompositions, reductions, etc., which the different materials 

 undergo, give rise invariably to the generation or absorption of heat. 

 In plain language, all chemical action produces heat or cold, according 

 to circumstances, and this production is in conformity with chemical 

 laws which are now fully understood. 



Among numerous chemical phenomena of this sort in the organism — 

 phenomena which have been thoroughly studied by M. Berthelot — special 

 reference may be made to hydrations, decompositions, combinations, 

 and fermentations. All these phenomena take place in the bodies of 

 living creatures, and all play their part in the process of calorification. 

 Calorification is then the result of multiplied chemical actions which oc- 

 cur at all points of the organism, actions of which some generate, while 

 others absorb heat, but among which those of the former evidently pre- 

 dominate. Among tlie heat-giving phenomena oxydations are the most 

 important, but it is well to remember that this is not their only attri- 

 bute, as Lavoisier believed. 



The simple fact that respiration is not carried on with the same 

 activity in all the tissues indicates a ^^riori that there must be an appre- 



