192 LIFE AND DEATH. 



the vital medium were the conditions of the juste 

 milieu. Water is wanted, there must not be too 

 much or too little. Oxygen is necessary, and also in 

 certain proportions. Heat is required, and for that, 

 too, there is an optimum degree. Certain chemical 

 compounds are needed and, in this respect too, there 

 must also be optima proportions. 



Water is a constituent element of the organisms. 

 They contain fixed proportions for the same tissue, 

 proportions varying from one tissue to another 

 (between | and ■^^. The cell of a living tissue re- 

 quires around it an aqueous atmosphere, formed by 

 the different juices of the organism, the interstitial 

 liquids, the blood, and the lymph. We are deceived 

 by appearances when we distinguish between aerial, 

 aquatic, and land-dwelling animals, and when we 

 speak of the air, the water, arid the land as their 

 natural environment. If we go to the bottom of 

 things, and fix our attention on the real living 

 unities, on the cells of which the organism is composed, 

 we shall find around them the juices, rich in water, 

 which are their real environment. If these juices are 

 diluted or concentrated the least in the world, life 

 stops. The cell, the whole animal, falls into a state 

 of latent life, or dies. " All living beings are aquatic," 

 said Claude Bernard. " Beings that live in the air are 

 in reality wandering aquariums," said another physio- 

 logist. " No moisture, no life," wrote Preyer. The 

 environment must contain water, but it must contain 

 it in certain proportions. In the higher animals 

 there is a mechanism which works automatically to 

 keep at a constant level the quantity of water in the 

 blood. Researches on the lavage of the blood (A. 

 Dastre and Loye) have clearly shown this. 



