Pathologist to Queen ChadotteJs and the Samardan Hospitals. (From the Pathological Laboratory of Queen Charlotte's Hospital.) I HAVE been for some months experimenting with a view to finding a quick and reliable method of estimating the amount of proteid in specimens of milk, usually from those cases where the children were not gaining, or getting on as well as might have been expected. The estimation of the fat is a comparatively easy process, but it is also necessary to know the percentage of

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... proteid, as it is quite possible that an excess or deficiency of this constituent may upset the child. The amount of sugar present I have found to vary so slightly that I do not consider the estimation of this substance of much importance. In estimating the proteid in the usual way by means of first estimating the sugar, the fat, and ash, and then deducting from the total solids, the difficulty is that it requires a considerable amount of experience to get exact results; one requires a lot of apparatus; it takes up a great deal of one's time, and it requires a much larger sample of milk than in the method I will presently describe, and in many cases where the infant is not thriving, and the supply of milk small, one can only obtain a few cubic centimetres of milk. Before reaching the process described below I tried all the wellknown precipitants of proteid, including phospho-tungatate, trichloracetic acid, etc. ; I also endeavoured to estimate the proteid by precipitating, and comparing the colour produced by adding the reagents which give definite colours with proteids; but I did not succeed in arriving at any satisfactory conclusion. I also tried by centrifugalising the precipitates in graduated tubes, rotating for definite times, and at the same rate of rotation, but this was found to be unsatisfactory, as even with two exactly similar preparations rotated at the same time the amount of precipitate read off was different, as the density of the precipitate varied; even an extra shake while adding the reagent, or the addition of the precipitant in slightly different ways, making all the difference. With large quantities of milk it might have been possible to do something with this method, but it was quite impracticable with small amounts.