A considerable number of large samples of woman's milk which was supposed to be the cause of the poor condition of the infants taking it have recently been analyzed at the Hospital for Sick Children to determine vwNhether or niot there was an abnormally high or low concentration of one or more of the salt constituents. The fat and total nitrogen content were also estimated in the samples when sufficient milk was available. The fat content was frequently found to be lower than normal but the nitrogen content, though tending to be slightly lower than average, never ran beyond normal limits. While this work was in progress the question arose whether the nitrogen distribution into the casein, lactalbumin and globulin, and non-protein nitrogen fractions might not in some cases show unusual values. Accordingly a series of determinations was made, not only in as many of the supposedly abnormal milks as possible but in a large number of samples of milk from wet nurses supplying the infant wards.The nitrogen distribution commonly taken as normal is that ascribed to Schlossman as quoted by Rietschell with calcium hydroxide and the removal of excess calcium as oxalate. This method was used in order to remove sugar and fat as well as protein, in preparation for applying their methods for estimating urea, amino-acids, etc. So far as could be ascertained the non-protein nitrogen fraction of the other investigators is the nitrogen content of the filtrate after precipitation in the milk with phosphotungstic acid. In the work here reported tannic acid was used as the protein precipitant, according to the procedure of L. L. Van Slyke9. It is claimed that cystin and the three basic amino-acids, lysin,arginin and histidin, are precipitated by phosphotungstic acid, as shown by D. D. Van Slyke in his scheme for the hydrolysis of proteins 10. In a number of the milks analyzed in this study tannic acid and phosphotungstic acid were each employed as precipitant. In all these the nitrogen content of the tannic acid filtrate was greater than that of the phosphotungstic acid filtrate by 0 5 to 6 0 per cent. of total nitrogen, the average being about 2 per cent.METHOIDS EMPLOYED.-The complete procedure in this study was as follows:-20 c.cm. of milk was accurately measured into a 50 c.cm. volumetric flask and diluted with distilled water about 1 in 2, 2 c.cm. of 2 per cent. acetic acid were added slowly with shaking, and the stoppered flask was allowed to stand in the cold for twelve hours or more. After being made to volume, the contents were filtered through a dry high grade filter paper and samples were measured out for total nitrogen estimation according to the Kjeldahl-Gunning method. In most of the other milks not agreeing with the infants extreme abnormalities were found in the content of fat or of one or more of the salt constituents.Thus it is seen that with one possible exception this entire series can be taken as showing a normal range of values for the casein, the combined lactalbumin and globulin, and the non-protein nitrogen f...
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