317 
or bluish white in color, is when separated known as “ skim milk.” 
; On account of changes due to the growth and action of micro-organ- 
! isms the color of the milk may be altered; for example, it has been 
I found under certain conditions to become red, blue, yellow, etc. As 
;[ is well known, milk when fresh possesses a distinctly sweet taste and 
’ a characteristic odor. It is heavier than water, the specific gravity 
; of cow’s milk ranging from 1.027 to 1.035. It freezes at a tempera- 
i ture somewhat lower than the freezing point of water — according to 
Beckmann (1), at —0.554° C. Atkins (2) has also found the freez- 
ing point of milk to be practically constant, viz, —0.55° C., the varia- 
tions from this mean value rarely exceeding 0.03° C. 
On account of the presence of dissolved salts of various kinds, milk 
conducts the electric current. Koeppe (3) found the electrical con- 
ductivity of cow’s milk to be 43.8. 10-^ and that of human milk to be 
22.6. 10-^. He concludes therefore that in cow’s milk 0.072 and in 
human milk 0.04 grammolecules (Molen) exist in the ionic condition, 
or, in other words, that in cow’s milk 58 per cent and in human milk 
26 per cent of the molecules are dissociated. 
The specific heat of milk has been determined by Fleischmann (4). 
For milk containing 3.17 per cent of fat he finds the specific heat to 
be 0.9457. This same author also determined the coefficient of 
expansion of milk by heat and found it between 5° and 15° C. to be 
greater than that of water. According to Fleischmann (5) milk 
shows no maximum of density above 1° C. 
The viscosity of milk has been determined by Soxhlet (6) using a 
Keischauer viscosimeter. The following are the ratios of the inter- 
vals required for the delivery of the same volume of water and milk 
at different temperatures: 
Temperature. 
Ratio of 
water 
to milk. 
Temperature. 
Ratio of 
water 
to milk. 
0° C 
100 : 221.1 
100 : 207.7 
100 ; 190.6 
100 : 188.7 
20° C 
100:211.7 
100 : 175.9 
100 : 169.0 
5° C 
25° C 
10° c 
30° C 
15° C 
The microscopic examination of milk reveals the presence of great 
numbers of fat globules, and according to Cohn (7) and also Savage 
(8) the presence also of leucocytes and streptococci derived from the 
udder of the cow. (For further information on this subject see 
article 13 of this bulletin, “ The significance of leucocytes and strep- 
tococci in milk,” by W. W. Miller.) 
Lawrence (79) has recently observed an instance of the appearance 
of typhoid bacilli in the milk of a nursing woman ill with typhoid 
fever. 
