in the sample can be estimated by the relative distance which the plates have been separated. [T] The British Society of Public Analysts regard the following as the _minimum_ proportions of constituents in unadulterated milk: Fat 2.5 per cent. Solids, not fat 9. " " ---- Total 11.5 " " Water 88.5 " " --_Trans._ The lactoscope possesses, however, but a limited degree of precision. _M. Marchand_ substitutes to its use the following tests: A test-tube is graduated in three equal divisions, the upper one being subdivided into hundredths extending above, in order to determine accurately the correct volume of the fluid, expanded, as it is, by the temperature of 40°, at which the examination is executed. The first division of the tube is filled with milk, a drop, or two of strong potassa lye added, and the mixture well shaken: the second portion is then filled with ether, and the third with alcohol. The mixture is next again thoroughly agitated, and then exposed to a temperature of 40° in a water-bath. After standing for several hours, a layer of fatty matter becomes sufficiently separated to allow of measurement: but, as it contains some ether and as a small amount of butter may still be retained in the lower aqueous fluid, a correction of the results obtained is necessary. M. Marchand has compiled a table, which facilitates this correction (_vide_: _Journ. de Pharm., Novembre 1854_, and _Bulletin de l'Académie de Médecine, Paris, 1854_, xix., p. 1101). Previously to the introduction of Marchand's apparatus, use was made of the _lactometer_, which consists simply of a graduated glass tube, in which the suspected milk is allowed to remain for 24 hours, at a temperature of 15°. After the lapse of this time, the cream present completely separates as a supernatant layer, the thickness of which indicates the quality of the sample taken. _M. Lacomte_ recommends the addition of glacial acetic acid, in order to cause the more rapid separation of the cream.