42 BIOLOGY. [Book i. 



coincides always in living beings, with a more elevated degree of 

 vitality, a greater molecular mobility. 



The action of certain chemical and physical agents on the 

 anatomical elements is in manifest relation with their constitu- 

 tion, In effect brought into contact with solutions of bichlorure 

 of mercury, of perchlorure of iron, of chromate of potash, of 

 alcohol, and of other substances eager in their thirst for water, 

 the anatomical elements lose their form and condense ; for they 

 then lose their constitutive water.^ It is for this reason that 

 alcohol definitively arrests the movements of the most resistant 

 of the animal elements, of the vibratile cells, of which we have 

 presently to speak, and that it kills in like manner the vibrions 

 and the spermatozoaries. 



Heat, on the contrary, first of all accelerates the vital pheno- 

 mena ; under its influence the mobile cells move with more 

 rapidity, the functions of plants ar^ accomplished with a greater 

 energy ; for a certain elevation of temperature facilitates the 

 chemical reactions and renders the osmosis more rapid. In like 

 fashion diffusion increases with temperature. For chlorohydric 

 acid we have in effect the following gradation : — 



Diffusion at 15° 5"== 1 



„ 27° = 1-3545 



„ 38° = 1-7732 



„ 49° = 2-1812 



But if the temperature continues to rise, the functional exci- 

 tation promptly reaches a maximum point, beyond which it first 

 of all decreases and soon is annihilated. Because the heat 

 diminishes by evaporation the constitutive water of the elements, 

 and alters the composition of the albuminoidal substances when 

 it does not coagulate them ; a result which is in-emediable. Sub- 

 jected to a temperature too elevated, the anatomical element soon 

 dies ; while cold, which likewise slackens and stops the nutritive 

 phenomena, does not always destroy them, sometimes merely 

 1 Ch. Eobin, Elements Anatomiques, p. 20. 



