134 NATURE AND LIFE. 



constant burning they are every instant receiving oxygen, 

 which brings about alterations of various kinds in the depth 

 of their substance. In a word, every organ breathes at all 

 its points at once, and breathes in its special way. Certain 

 physiologists of the present day are wrong in localizing the 

 phenomena of breathing in the capillary vessels. They are 

 merely the channels of transfer for oxygen, which, by exos- 

 mosis, penetrates their thin walls, and then effects, by di- 

 rect contact with the smallest particles of the organized 

 mass, the chemical action which keeps up the fire of life. 

 It is easy to prove this by placing any tissue, lately de- 

 tached from the body, in an oxygenated medium. We re- 

 mark in this case an escape of carbonic acid, together with 

 a development of heat, and this possibility of breathing 

 outside the system proves clearly that such act can be ac- 

 curately compared, as Lavoisier thought, to the combustion 

 of any substance. The only difference is with regard to in- 

 tensity. While a candle or a bit of wood burns rapidly, 

 with a flame, the combustible materials of organic pulp 

 unite with oxygen in a more slow and quiet manner, less 

 violently and manifestly. 



The blood, which flows and reflows incessantly in the 

 most slender vessels of our bodies, and charges itself full 

 with oxygen every time the chest heaves, is composed of 

 very various substances. It contains mineral salts, such 

 as chlorures, sulphates, phosphates of potassium, soda, 

 lime, magnesia, coloring-matters, fatty particles, neutral 

 substances of the nature of starch, and nitrogenized prod- 

 ucts, such as albumen and fibrin. The salts undergo slight 

 changes in the torrent of circulation ; they are eliminated 

 by the chief emunctories. The neutral matters of the na- 

 ture of starch are converted into glycogene and fat. The 

 fatty particles undergo in the blood only such oxidizations 

 as produce certain derivatives of the same order. And, 

 last, the nitrogenized products are made over into fibrin, 



