SOLANUM TUBEROSUM. 
for arrow-root, and is also so manufactured as to resemble and 
be sold for sago. The tissue of potatoes is cellular,—each cell 
contains from ten to twelve grains of starch. Both in the cells 
and in the intercellular spaces is an albuminous liquid. By 
boiling the cells are separated, the starch-grains absorb the al- 
buminous liquid, swell up, and completely fill the cells, while 
the albumen coagulates and forms irregular fibres, which are 
placed between the starch-grains. Potatoes in which these 
changes are complete, are called meally, while those in which 
the liquid is only partially absorbed, acd the coagulations im- 
perfectly effected, are denominated doughy, or watery. 
Potatoes have been repeatedly subjected to chemical examina- 
tion ; their principal constituents are starch, starchy fibrin, al- 
‘ie gum, acids, salts, and water. The relative proportions 
vary with the season, the varieties of the potatoe, &c. Potato- 
starch consists of particles of varied shapes, and sizes—the nor- 
mal form is probably ovate. Their size varies from one six- 
hundredth to one thirtieth of a line in diameter. They are 
characterized by concentric rings, observed on their surface, and 
which Fritzche regards as indications of concentric layers, of 
which he asserts these grains to be composed. The hilum is 
circular. The cracks observed on some of the danger grains 
proceed usually from the hilum, 
‘Sugar is sometimes manufactured from potatoes. By fer- 
mentation potatoes yield a vinous liquid (potato-wine) of good 
quality. By distillation this yields potato-spirit, from which a 
volatile oil (ot of potatoes) has been extracted. An extract 
obtained from the stalks and leaves of potatoes is said to possess 
narcotic properties, in doses of two or three grains, but the cases 
are not perfectly satisfactory. 
The tubers of potatoes when boiled are a most valuable article 
of food, both for men and animals. Those of good quality are 
_ not only perfectly innocuous but highly nutritious, and easy of 
digestion. In the raw state they have been found less nutri- 
tive for animals, while on man they are said to prove laxative 
and diuretic, and to excite slightly the nervous system. The 
process of cooking is probably useful in two ways, by rendering 
_ the starch. digestible, and secondly by extracting some noxious 
Matter. The potato in a raw state, eaten as a salad with vin- 
egar, has proved of much benefit on ship-board as a preventative 
of scurvy. An extraet of the leaves is recommended in chronio 
Pheumatin, and paises of the stomach and bowels. 
