DIGESTION. 
thefe properties muft alfe be of a compound nature, that ic, 
mutt contift of feveral elements, otherwife they would be inca- 
pable of the Siw 2d decompofition: they mn4 alfo have al- 
ready exper i 
the eieag a€ticn of the organs of maftication and in- 
falivation. 
of man takes in almoft every variety of bot 
animal and vegetable fubltances. It confilts therefore of ie: 
al unchangeable principles, saga te to the bufinefs of nu- 
trition, combined with others in w 
at Tt i rtions. 
n, albumen, Feoula, fibrine, fugar, 
e of oxalic acid, are the general moditications 
under which the nutritive fubftance prefents itfelf, Each 
of thefe varies according to the nature of the heterogeneous a 
principles with which it is affociated. 
e numerous plante which do a@iually, or which might 
ferve for food, mucila, ze fometimes exifts alone, or ps 
Qu 
Im per diy (ied, whiie in the other it is brought into a 
very hoa volu 
tragacanth, iar cherry-gum, &c. are examples 
of this matter. o where cultivated, nor even collected 
for food ; fo that we ee be apt to eonfider 1 it as incapa- 
ble of allording any nourifhment, if it were nct known that 
the caravans creffing the fandy deferts of Africa, over which 
they have brought gum feneca, have in many inltances loft 
their way, exhaufted their provifions, and been obliged to 
ive on this gum for many weeks, having ee elle but 
water alone, and a very faring fupply o Mucilage 
vegetable juices, nd in the*ftems 
9 
various degrees of tenacity and Ste 
in which i 6 decemaiies all the ea arpa > the 
whit Ni fara which contain an abundance of gelatine. In 
d, it forms the animal jellies, which: conftitute a ad. 
fight, om wholefome food. 
egetable gluten is always found combined with ether 
Thies foluble in water, without sits it could not be 
Giffolved i in, and blended with, our jui It abounds in 
the gramina, where it is united with Fecula, extractive prin- 
a oe matter, mucilage, and an earthy fubftance. 
Ibumen of animal matters refembles, in many points, 
the Geeiaule gluten. The whole white, and a great part 
of the yolk of an egg, are a compofition of albumen, a | co» 
e cafeous matter of milk is is a 
oxious, 
Wheat is compofed of gelatinous mat- 
Thefe two principles, acted on by the 
mentative procefs, form bread, the nutritive qualities of 
which are not furpafled by any fabilanee. It is fo much 
Vou. XI, 
the more proper for animalization, inafmuch asthe ferment. 
ation has already brought it into a ftate fit for decompofi 
tion. 
e principle now alluded to, which conftitutes the fari« 
although not u probably, in the 
ftems of fome ne, ae the exprefled 
juice of which fago is formed ; in the roots of many claffes, 
as the potatoe, yam, and pignut, in which it is very 
abundant. 
The fibrine of the mufcles and blood partakes of the pro- 
perties of giuten and fecula: it admits of a very ipeedy affie 
aria 
a clo ut delicate and divifible texture, in the 
oat, of wane — ate h form alight and fucculent 
kind of food. An extradtive colouring matter generally ad- 
heres to the fibrous aula. ; and the differences in its quan- 
tity or quality nes the appearance and nutritive powers 
of our various animal foods. 
Sugar, and the oxalic bafe, which can hardly ke feoarated 
from it, are produced by both kingdoms. ‘lhe vegetable 
acids are convertible into a fugary fubRance, which beltows 
on them whatever nutritive powers they may poflcfz. Other 
acids, befide the oxalic, are unfit for n-urifhment ; and they 
only acquire that property by an admixture of the latter or 
of {ngar or mucilage. ‘The fame principles ex'{t in varions 
ere e 
hare of m cid, and water, indicate how 
ar they are foteepritle of cree tees and, confrquently, nou- 
5 
§ 
co 
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me 
= 
rt 
ie: 
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mt 
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ad 
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But the three 
of the African tribes, grapes in fome part tugal and 
reece ie the Grecian iflar 
vegetables, are ail “capable of 
Bae *digeled 5 the feeds evan them ” efpecially 
nuts, are in many inftances the prin cipa al Cae f the inhae 
i oaenuts in America a the Fall. 
afford nourishment ; the 
fource of thefe is ee fat of meat and butter, but there are pers 
ns who drink with avidit {permaceti and trasn oil. 
owThe fmall number of principles juft enumerated, as afcer- 
tained by the refearches of modern chemiltry, fix the pariti- 
cular characters on which the natural diflinGiione of our ali- 
ments — reft. The numerous modifications ee thefe 
undergo, from a variety of caufes, will in@uence our 
choice of particular Species of ood. but thefe coniderations 
4 
EE 
