662 MILK. 



Woman's milk also contains lactalbumin, besides the casein, and a protein 

 substance, very rich in sulphur (4.7 per cent) and relatively poor in carbon, which 

 WROBLEWSKY calls opalisin. The statements as to the occurrence of proteoses and 

 peptones are conflicting as in many other cases. No positive proof as to the 

 occurrence of proteoses and peptones in fresh milk has been given. 



Because of the properties and low amount of casein in human milk 

 it is often difficult to precipitate it, with acid, and to prepare it, but 

 this can easily be accomplished by dialysis. A number of methods 

 have been suggested for the preparation of human casein. FULD and 

 WOHLGEMUTH recommend the freezing of the milk previous to pre- 

 cipitation, so that the casein masses become larger to a certain extent 

 and the precipitation becomes easier. ENGEL l recommends dilution 

 with water to 5 volumes, and the addition of 60-80 cc. N/10 acetic acid 

 for each 100 cc. milk. The mixture is first cooled for 2-3 hours and then, 

 after shaking, warmed on the water-bath to 40 for a few minutes. 



Even after those differences are eliminated which depend on the imper- 

 fect analytical methods employed, the quantitative composition of woman's 

 milk is variable to such an extent that it is impossible to give any average 

 results. The numerous analyses, especially those made on a large number 

 of samples by PFEIFFER, ADRIANCE, CAMERER and SoLDNER, 2 have posi- 

 tively shown that woman's milk is essentially poorer in proteins but 

 richer in sugar than cow's milk. The quantity of protein varies between 

 10-20 p. m., often amounting to only 15-17 p. m. or less, and is dependent 

 upon the length of lactation (see below). The quantity of fat also varies 

 considerably, but ordinarily amounts to 30-40 p. m. The quantity of 

 sugar should not be below 50 p. m., but may rise to even 80 p. m. About 

 60 p. m. may be considered as an average, but it should be borne in mind 

 that the quantity of sugar is also dependent upon the length of lactation, 

 as it increases with duration. The amount of mineral bodies varies 

 between 2 and 4 p. m. 



The division of the total nitrogen in human milk is, according to A. 

 FREHN, S very variable. As approximate average figures we can say 

 that 40-45 per cent of the total nitrogen is casein, 35-40 per cent remain- 



Bestandteil der Milch, Anzeiger der Akad. d. Wiss. in Krakau, 1898; Kobrak, Pfluger's 

 Arch., 80; Langstein and Bergell, cited in Bioch. Centralbl., 8, 323; Langstein and 

 Edelstein, Maly's Jahresber, 40, 254; Abderhalden and Langstein. Zeitschr., f. physiol. 

 Chem., 66. 



1 Fuld and Wohlgemuth, Bioch. Zeitschr., 5; Engel, ibid., 14. 



2 Pfeiffer, Jahrb. f. Kinderheilkunde, 20, also Maly's Jahresber., 13; V. Adriance 

 and J. Adriance, A Clinical Report of the Chemical Examination, etc., Archives of 

 Pediatrics, 1897; Camerer and Soldner, Zeitschr. f. Biologic, 33 and 36. In regard 

 to the composition of Woman's milk, see also Biel, Maly's Jahresber., 4; Christenn, 

 ibid., 7; Mendes de Leon, ibid., 12; Gerber, Bull. soc. chim., 23; Tolmatscheff, 

 Hoppe-Seyler's Med.-chem. Untersuch., 272. 



3 Zeitschr. f. physioi. Chem., 65; see also Engel and Frehn, Maly's Jahresber., 40. 



