246 



Food and its Digestion. 



" Liquidum non rum-pit jejunum" and consequently per- 

 mitted his devout co-religionists to fast on the very stiffest 

 of chocolate as being drink and not food. 



Physiology declines to distinguish between food and 

 drink, or if it use the latter word at all, would limit it 

 to distilled water devoid of all dissolved solids. Drink 

 then in the physiological sense is included in food. 



The most natural division of food would be into the 

 animal, vegetable, and mineral substances. 



These three kingdoms of nature all contribute to the 

 sustenance of man. 



In the cold regions of the earth, he lives almost wholly 

 on animal and mineral food. In hot climates on vegetable 

 and mineral, and in the temperate regions his food is 

 from the animal and vegetable kingdoms, mingled with a 

 due proportion of inorganic matter. 



It is very difficult to make any classification of those 

 substances taken as food which is altogether unobjec- 

 tionable. It has been attempted on a supposed physiolo- 

 gical basis, dividing the substances into the histogenetic, 

 or those supposed to aid solely in the formation of the 

 tissues, and the calorifacient, those maintaining the heat 

 of the body. But such exclusive division is not practica- 

 ble, because it is now known that those substances which 

 are preeminently tissue forming or histogenetic (likewise 

 contribute to produce heat), and those which are mainly 

 calorifacient in their action — heat producers — also con- 

 tribute to the formation of the tissues. 



A more convenient classification is based upon the 

 predominance in the food of some one or more of the ele- 

 ments which give an individuality to the group of articles 

 in which they are found. 



Food of every variety when analysed is resolvable into 

 four elements, which are carbon, hydrogen, oxygen and nitro- 

 gen, combined with certain minerals. These, in the great 

 balance of organic nature, whether in the atmosphere, in 

 water, in plants or in animals, play the principal part. 



