64 FOOD. 



ment to animals in some degree, but subordinately to matter 

 which has belonged to vegetables or animals, and that it alone will 

 in some instances support life for a time. Vegetables live chiefly 

 on such, and will indisputably live for a time with facility on them 

 alone, and some even if merely suspended in the air 1 (carbonic 

 acid is, indeed, the great nourishment of all vegetables), but even- 

 tually will not thrive and perfect their seed, unless animal or 

 vegetable remains exist in the soil ; whence the necessity of this 

 kind of manure, which must have likewise been so changed by 

 putrefaction that its carbon has formed a compound resembling 

 the extractive principle and thus capable of solution in water. 

 It has been contended that some animals, as fish, and that some 

 vegetables, readily subsist, growing equally with others, and per- 

 fecting their seed or ova, on simple water ; but the experiments 

 in support of this assertion are not at all decisive. None of 

 these statements are affected by the derivation of gaseous sub- 

 stances from the surrounding air or water, by animals or vege- 

 tables. 



The articles of diet generally employed by every nation and 

 class of society are much determined by the facility with which 

 they are procured. Generally, too, animal food is preferred in 

 cold climates, and vegetable in warm : a mixture, however, of the 

 two is usually preferred to either exclusively, and appears better 

 suited to our necessities. Animal food is chiefly muscle and fat, 

 milk and eggs ; vegetable food, chiefly seeds and roots, fruits and 

 leaves, with more or less of the stalks. These articles, which are 

 rendered more or less masticable or digestible by heat, are 

 previously subjected to high temperatures in various ways ; and 

 as many saline and aromatic substances are taken, not so much for 

 their nutritive qualities and their undoubted assistance when the 

 stomach is weak or chiefly vegetables are eaten, as for their sapid 

 qualities, and since the admixture of these, and the combination 



1 Two fig plants ( Ficus austraUs and Ficus elastica) have continued to send 

 out shoots and leaves, the former for eight, the latter for fourteen, years, sus- 

 pended in the hot houses of the Botanical Garden of Edinburgh. Elements of 

 Chemistry, by Dr. Turner, Professor of Chemistry in the University of London, 

 1833. p. 862. sq. 



171 Mould consists principally of carbon, combined with a little oxygen and 

 hydrogen, and, if it be animal, with also a little azote, together with the usual 

 saline ingredients of organised substances. 



n Full information on this subject will be found in Dr. Thomson's System of 

 Chemistry, book iv. ch. 3. sect 2. 



