480 MEALS MEDICINAL. 
aus oi percent me Ser SO re art Setar ae 
adult life this is not desirable. Yet, among Modern Methuselahs 
(Bailey), more than one centenarian is told about, who by eating 
but little substantial food, and only drinking milk, reached the 
great age of one hundred and thirty-eight vears, whilst no hearty 
meat-eater has got beyond one hundred and three years. 
The casein, or curd of these milks, is an albumin, but 
distinguished from other albumins by becoming coagulated 
when swallowed, through the action on it of the gastric juice, 
but not by heat when cooked, as the albumin (or white) of egg 
does. And the casein of one animal differs from that of another. 
This is the chief proteid, or nitrogenous constituent of milk, 
not coagulating spontaneously, as the fibrin, or albumin, of blood 
does, but by the action of acids, and of rennet. The casein of 
milk yields no uric acid, and does not contain any nuclein, which 
fact renders it specially of service for goutily disposed persons 
as a food; and it yields no carbohydrate when split up, which 
may render it of particular value in those severe cases of diabetes 
in which sugar is formed out of proteid foods. Curdling of milk 
depends on the production of lactic acid in the milk, which turns 
the curd, or casein, out of its partnership with the lime salts ; 
then the casein, not being soluble, falls down as a flocculent 
precipitate, or clot. Lactic acid is formed in sour milk, this 
being, when concentrated by the chemist, a syrupy, intensely 
sour liquid, comprising well-defined salts. (It is produced 
likewise in the fermentation of several vegetable juices, and 
during the putrescence of some animal matters). Nevertheless, 
milk is the most powerful preventive of acidity, or neutralizer 
of acid, among all foods, chiefly by its citrate of lime, the basis 
of which is identical with that of lemon-juice; fer a good cow 
yields practically as much citric acid in a day, as would be con- 
tained in two or three lemons. This citrate of lime, as occurring 
in new unboiled milk, is altogether devoid of any sour taste. 
The solid particles sometimes met with in Condensed 
Milk consist chiefly of this citrate of lime. The great majority 
of condensed milks are sweetened by the addition of cane sugat 
(indigestible by an infant) in considerable quantity, so as to 
preserve them unchanged after the cans have been opened. 
Children fed on condensed milk get their teeth late, and are 
likely to be rickety; they become plump, but paddy ; large. 
but not strong, lacking the power of endurance, and of resistance 
to disease. The condensed milk, when used for emergencies, 
