The percentage of sugar, salt, caseine, butter, etc., were ascertained, and the results noted on the certificates given you, but have not been included in the statement above. The method of analysis which I have pursued is as follows:

1. REACTION OF THE MILK. Good milk is slightly alkaline; sometimes carbonate of soda is added to milk to prevent it from becoming sour; in such cases, the milk has strong alkaline reaction, and effervesces slightly on the addition of acids.

2. CREAM. A quantity of milk is poured into a tube graduated to one hundred parts. On standing for twenty-four hours, the cream rises to the surface, and its amount ascertained from the number of divisions which it occupies. The amount of cream, of course, varies considerably in different samples, depending, as is well known, upon the care of the animal, the feed, the season, and many other circumstances. In hot countries, and dry seasons, the quantity of milk yielded is less, though its quality is said to be better. It is also stated that

cold favors the production of sugar and cheese, while hot weather augments the amount of butter. The average amount of cream is nine and one-half per cent, by volume.

3. SPECIFIC GRAVITY. The specific gravity of pure milk averages 1.030, although the percentage of cream, being itself variable, and lighter than water, necessarily affects the specific gravity to some extent, producing variations between 1.026 and 1.035.

4. AMOUNT OF SOLID CONSTITUENTS AND INORGANIC SALTS. A quantity of milk is dried at 212° Fahrenheit. The weight of the residue shows the amount of all the solid constituents. The residue, when ignited, loses its organic constituents, butter, caseine, milk, sugar, etc., leaving the inorganic or mineral salts behind. Carbonate of soda, used to keep the milk from souring, is found in this residue.

5. BUTTER. A certain quantity of milk is soaked up in sand and dried at 212° Fahrenheit. The residue is treated with ether. The ether, on its evaporation, leaves the butter. The total amount of solid constituents, less the butter and inorganic salts, gives the amount of caseine and sugar.

When milk is adulterated, the adulterating material is almost invariably water. Books on this subject enumerate various articles which are sometimes added to milk, as chalk, sheep's brains, starch, flour, etc. That these substances have been occasionally though rarely used there is no doubt, though I have never been able to detect any of these substances. Chalk would readily be detected by its insolubility; starch by iodine; cere. bral matter by the microscope, etc. It is extremely doubtful if any one, in this vicinity, at least, has ever made use of any of those unscientific and readily detected adulterations, which it has been so often asserted have been found in milk. Salt is

sometimes added to increase the specific gravity, which has been reduced by the addition of water. Burnt sugar is used to alter the blue tinge which watered milk possesses, and carbonate of soda to prevent souring, as has been stated; but beyond these, water is the only practical adulterant of milk. This adulterant, it is true, is not directly injurious, but it is no light matter to rob an important article of daily food like milk of a large portion of its nutritious constituents. As has been remarked, “milk, adulterated with water, is milk no longer; and, although the agent is of itself harmless, its use in this way is no less a grave offence both against the health and pockets of the community.

Water is detected by a comparison of the amount of the solid ingredients in the sample of milk examined and the amount in cow's milk of average quality. Pure cow's milk may be considered as having never less than 12.5 per cent of solid matter. If pure milk then contains 12 parts solids, a sample of milk having less will contain only the percentage of pure milk expressed by the proportion the amount of solids in sample bears to 121; the rest is added water. Thus, a pure milk containing water 87.5, solids, 12.5, if adulterated so that it contains only equal parts, pure milk and water, would give an analysis, water 93.75, solids, 6.25. The percentage of water in milk may also be determined from the amount of sugar contained in sample.

In closing, our acknowledgments are due to the courts, officers and others, for their coöperation in the objects and purposes of this office.

Respectfully submitted,

HENRY FAXON, Inspector.

CITY HALL, BOSTON, April 1, 1870.