The foregoing brief statements suffice to show the importance of the dairy and its products in connection with the subject of food, even when considered apart from the question of their dietetic value. I shall next proceed to describe the composition and characteristics of good milk, adding some remarks on its use as diet, and then indicate the practical mode in which those who are interested in obtaining it unadulterated and uncon- taminated may obtain their object.

The following analysis of an average sample of pure cow's-milk is the result of the most recent researches, and varies in some important particulars from analyses made at an earlier date:

The chief difference to be remarked consists in the reduced estimate of the Proteids as compared with the estimates before made.*

* I am indebted to the valuable encyclopaedic treatise entitled "Food and the Principles of Dietetics," by Robert Hutchison, M.D., M.R.C.P., Assistant Physician to the London Hospital and to the Hospital for Sick Children, Great Ormond Street (E. Arnold, London, 1900).

Composition of milk.

The specific gravity is generally about 1030 to 1033, at 6o° Fahr.; but specific gravity alone cannot be regarded as an exact test of quality, since the quantity of cream varies with different specimens; and as cream is of lighter specific gravity than milk, a specimen of the latter, which is extremely rich in cream, other ingredients being the same, will weigh lighter than one which is deficient in cream. But that a sample of milk exceptionally rich in cream should be offered for sale, although hypothetically possible, must be regarded as practically impossible in the last degree. The nutritive value of milk corresponds, of course, with the aggregate amount of all the solids contained, and for all purposes of the consumer, the specific gravity corresponds with that amount, the figure rising as the solids are augmented.

The specific gravity of unadulterated milk furnished by different healthy cows may be regarded as ranging between 1027 and 1035. But the mixed product of several such cows equals at least 1030 or 1031. If the milk furnished by any dealer is persistently below 1030, there is ground for complaint on the part of the customer; and I think it may be said that any metropolitan dairy of repute will furnish a uniform supply of milk decidedly above 1030. Nevertheless, there is a large quantity sold by the small dealers to the poor, of which the specific gravity is no more than 1025 or 1026. Nothing, however, is easier than to ascertain the real value of any sample which the purchaser desires to test. A lactometer may be bought for 2s. 6d.: it is only necessary to float it in a jug of milk, and the figure on its scale, which is level with the surface of the milk, is the specific gravity; the temperature should be about 6o° Fahr.

Specific gravity.

Consideration in relation to.

Amount of solids is the measure of value.

Analysis of Milk.

Where an exact analysis is required, as, for example, to determine the question of fining a fraudulent dealer, the value of the sample has to be found, by ascertaining the amount of solids present, apart from the cream, and estimating the latter separately.

The Society of Public Analysts requires a minimum of "nine per cent, of solids, not fat;" and any sample which does not reach that amount has almost invariably been adulterated with water, and the seller of it is liable to a fine. But "nine per cent." is a low standard determined on to avoid the infliction of hardship on any small dealer who may have been supplied from the country with a genuine, though exceptionally poor milk, of which the solids did not exceed nine per cent.; and it may probably yet be altered. Hence, vast quantities of milk which are sold every day at that standard, contain a good deal of added water.

The standard of the best metropolitan dairies, whose interest it is to supply unadulterated milk, is always higher.