/ '///: /■: l TS OF - UILK. r 3 3 
with acid. Landwehr ' identified it as animal gum, B^champ 2 as dextrin. 
J. Herz 3 found granules in milk, which behave towards iodine like starch; 
he called them "animal amyloid." 
The fats of milk. — Milk fat has a specific gravity of from 949 
to 996. * It consists of palmitio, stearin, and olein, with small quantities 
of triglycerides of butyric, caproic, caprylic, capric, myristic, and arachic 
acids in addition. 5 It also contains small quantities of Lecithin, choles- 
fcerin, and a yellow lipochrome. 
The aim mnt of fat in cream varies from 14 to 44 per cent. In butter, 
besides lit, there are small quantities of caseinogen and lactose. The 
fats of cows' butter consist of 68 percent, of palmitin and stearin. 30 
per cent, of olein, and 2 per cent, of the specific butter fats. 6 Their 
melting point is 3 l°to .".4" C. The volatile fatty acids in cows' milk, acci ir< 1 - 
ing to Duclaux, 7 amount to 7 per cent., of which 3'7 to 54 is butyric, and 
2 - to :!••"> is caproic acid. Some analysts give still higher percentages. 
By exposure to the air butter becomes rancid; this is partly due to 
the production of lower fatty acids from the higher fats (see p. 19), 
partly to the formation of acrolein from glycerine, and partly, and 
according to Hagemann chiefly, to the formation of lactic acid from the 
entangled lactose. 
The composition of butter is very variable. Thus, in Finland butter, 
Koefoed s found two fatty acids of the acrylic series in addition to oleic 
acid; 100 parts of the fatty acid contained 66 of these acids, 28 of 
palmitic, 22 of myristic, 8 of lauric, 1*5 of butyric, 2 of caproic, 2 of capric, 
and 0*5 of caprylic acid. According to Wanklyn, 9 there is no true palmitic 
acid in butter; the acid is aldepalmitic acid (C\ 6 H 30 O.,). 
The fats of human milk are somewhat different from those of cows' 
milk. They have been the subject of two recent researches — one by 
Ruppel, 10 the other by Laves. u 
Their melting point i< 34° C, and solidifying point 20 o- 2 C. Their 
specific gravity at 15° C. is 966. The fatty acids found are butyric, 
caproic, capric, myristic. palmitic, stearic, and oleic acids, all combined 
with glycerine. The presence of formic acid 12 is also inferred from its 
reducing action, but not by any further tests. Human milk is poor in 
volatile acids (Ruppel). 
Laves confirms this work, and gives some quantitative results. The 
fat contains 14- per cent, of volatile acids, 1'9 of acids soluble in water, 
and 49 - 4 (a very high percentage) of unsaturated acids. The volatile 
1 Arch. f. d. gcs. Physiol., Bonn, Bde. xxxix. and xl. 
-Ball. Soc. chim., Pari.-. Ser. 3, tome vi. 
:J ''hem. Ztg., Cbthen, Bd. xvi. S. 1594. 
4 Bohr, Jahresb. u. >1. Fortschr. '1. Thier-Chem., Wiesbaden, Bd. x. S. 182. 
5 Grunzweig, Ann. 'I. Ohem., Leipzig, Bd. clxii. S. 215: E. Wein, Diss., Erlangen, 
1876; Chevrenl, " Reclierches sur le corps gras," Paris, 1823; Lerch, Ann. d. ' 
Leipzig, Bd. xlix. S. 212 ; Heintz, ibid., Bd. lxxxviii. S. 300. 
6 Bromeis, ibid., 1842, Bd. xlii. S. 46. 
pt. rend. Acad. d. sc, Paris, tome civ. 
8 Overs, o. d. ]c. Dansi . Selsk. Fork., Kjobenhavn, 1891. 
9 Chem. X> ws, London, vol. lxiii. 
}° Ztschr.f. Biol.. Miinchen, Bd. xxxi. S. 1. 
11 Ztschr. f. physiol. Ohem., Strassburg, Bd. xix. S. 369. 
12 Duclaux {loc. cit.) found formic acid in cows' butter which had been exposed to 
sunlight. 
