140 THE INFLUENCE OF INANIMATE SUKHOUNDINSS. 



CHAPTEE V, 



THE INFLUENCE OF STAGNANT WATEK. 



The media surrounding the animal, and in wHcli it lives, are 

 sometimes gaseous, as the atmosphere, sometimes fluid, as the 

 water of the sea or of rivers, sometimes even solid ; these last, 

 as earth, wood, stone, <fec., may be considered as absolutely 

 motionless with regard to the animal, since they can only influ- 

 ence the creatures that live in them by their varying hardness 

 or their chemical changes. Gaseous or fluid media cannot be 

 regarded as perfectly inactive ; they are capable of certain swift 

 modes of motion, known as currents or as winds. Hence we 

 are compelled to investigate the influences of water and air on 

 the animals that live in them under two separate heads, ac- 

 cording to whether the air or water is stagnant or in motion, 

 since they influence animals quite differently in these two dif- 

 ferent states. Moreover, we must separate our enquiries as to 

 the effects of air from those as to the effects of water, for they 

 affect the animal world very differently. I shall begin the dis- 

 cussion of the whole subject with such facts and experiments as 

 illustrate the selective or transforming influence of stagnant 

 water. 



I. General preliminary remarks. — Water is an indispen- 

 sable condition of animal life. A frozen-up frog, fish, or egg of 

 an insect is leading only a latent, not an active life. In pro- 

 toplasm, the essential living constituent of every animal cell, 

 there is a great quantity of water; if it is all extracted by 

 drying, the cell ceases to live. The old statement is well known, 

 ' Corpora non agunt nisi fluida.' But the universal eflfects of 

 a condition of life which is equally indispensable to a single cell 



