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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 :
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 emploj’ed, 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,3
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.. 06.
1
Fuld and Wohlgemuth, Bioch. Zeitschr., 5; Engel, ibid., 14.
2
Pfeiffer, Jahrb. f. Kinderheilkundc, 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. Biologie, 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; Cerber, Bull. soc. chim., 23; Tolmatscheff,
Hoppe-Seyler’fl Med.-chem. Untersuch., 272.
Zeitschr. f. physiol. Chem., 65; see also Engel and Frehn, Maly’s Jahresber., 40.
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