RESULTS OF LIFE 257 



manure, the essential function of which is to keep up a favourable 

 moisture round about the roots of plants. 



Animals cannot build up direct combinations like plants : hence 

 they use compound substances for food ; they have to carry out 

 digestion (at least nearly all of them), and they consequently have 

 organs for this purpose. 



But they also form for themselves their own substance and secre- 

 tions : now for this purpose they are not obliged to use as food either 

 these secretions, or a substance like their own : out of grass or hay 

 the horse forms by the action of its organs its blood and other humours, 

 its flesh and its muscles, the substances of its cellular tissue, vessels 

 and glands, its tendons, cartilages and bones, and lastly the horny 

 matter of its hoofs, and the hair of its body, tail and mane. 



It is then in forming their own substance and secretions, that animals 

 build up to a high degree the combinations that they produce, and give 

 to these combinations the astonishing number of principles that enter 

 into animal substances. 



Let us now remark that the substance of living bodies, as also the 

 secretions which they produce by their organic activity, vary in 

 quality according to the following circumstances : 



1. The actual nature of the living being which forms them : thus 

 vegetable productions are in general différent from animal productions ; 

 and among the latter the productions of vertebrates are in general 

 different from those of invertebrates. 



2. The nature of the organ which separates them from other sub- 

 stances after their formation : the secretions of the liver are not the 

 same as those of the kidneys, etc. 



3. The vigour or debility of the organs of the living being and of 

 their action : the secretions of a young plant are not the same as those 

 of the same plant when it is very old ; nor are those of a child the 

 same as those of a grown man. 



4. The integrity of the organic functions : the secretions of a healthy 

 man cannot be the same as those of a diseased man. 



5. The abundance of caloric which is continually formed on the sur- 

 face of the earth although in quantities varying in different climates, 

 and which favours the organic activity of the living bodies which it 

 penetrates ; or the rarity of caloric, as a result of which this organic 

 activity is greatly enfeebled : as a matter of fact in hot climates the 

 secretions formed by living bodies are different from those that they 

 produce in cold climates ; and in cold climates again the secretions 

 of these bodies differ among themselves, according as they are formed in 

 the hot season or during the rigours of winter. 



I shall not here further emphasise the fact that the organic action 



