uices, such as
produce sickness, or evacuate the bowels, or such even as are only
disagreeable to the palate, appear to be a part of the defence of those
vegetables, which possess them, from the assaults of larger animals or of
insects. As mentioned in the Botanic Garden, Part II. Cant. I. line 161,
note. This appears in a forcible manner from the perusal of some travels,
which have been published of those unfortunate people, who have suffered
shipwreck on uncultivated countries, and have with difficulty found food to
subsist, in otherwise not inhospitable climates.

4. As these acrid and intoxicating juices generally reside in the mucilage,
and not in the starch of many roots, and seeds, according to the
observation of M. Parmentier, the wholesome or nutritive parts of some
vegetables may be thus separated from the medicinal parts of them. Thus if
the root of white briony be rasped into cold water, by means of a
bread-grater made of a tinned iron plate, and agitated in it, the acrid
juice of the root along with the mucilage will be dissolved, or swim, in
the water; while a starch perfectly wholesome and nutritious will subside,
and may be used as food in times of scarcity.

M. Parmentier further observes, that potatoes contain too much mucilage in
proportion to their starch, which prevents them from being converted into
good bread. But that if the starch be collected from ten pounds of raw
potatoes by grating them into cold water, and agitating them, as above
mentioned; and if the starch thus procured be mixed with other ten pounds
of boiled potatoes, and properly subjected to fermentation like wheat
flour, that it will make as good bread as the finest wheat.

Good bread may also be made by mixing wheat-flour with boiled potatoes.
Eighteen pounds of wheat flour are said to make twenty-two pounds and a
half of bread. Eighteen pounds of wheat-flour mixed with nine pounds of
boiled potatoes, are said to make twenty-nine pounds and a half of bread.
This difference of weight must arise from the difference of the previous
dryness of the two materials. The potatoes might probably make better
flour, if they were boiled in steam, in a close vessel, made some degrees
hotter than common boiling water.

Other vegetable matters may be deprived of their too great acrimony by
boiling in water, as the great variety of the cabbage, the young tops of
white briony, water-cresses, asparagus, with innumerable roots, and some
fruits. Oth