311 
isms the color of the milk may be altered; for example, it has been 
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 
temperature somewhat lower than the freezing point of water — 
according to Beckmann (1), at —0.554° C. On account of the pres- 
ence of dissolved salts of various kinds, it conducts the electric cur- 
rent. Koeppe (2) found the electrical conductivity of cow’s milk to 
be 43.8. 10- 4 and that of human milk to be 22.6. 10- 4 . He concludes 
therefore that in cow’s milk 0.072 and in human milk 0.04 gram- 
molecules (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 (3). 
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 (4) milk 
shows no maximum of density above 1° C. 
The viscosity of milk has been determined by Soxhlet (5) using a 
Reischauer 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 (6) and also Savage (7) 
the presence also of leucocytes and streptococci derived from the udder 
of the cow. With the higher powers of the microscope various forms 
of bacteria can be distinguished, some of which at least play an im- 
portant part in the changes which take place when milk is kept for 
some time at ordinary temperatures. The perfectly fresh milk of 
carnivorous animals is as a rule acid in reaction. According to 
Leach (8) the acidity of fresh milk is due to carbon dioxide and acid 
phosphates, and according to Richmond (9) to mono- and di-phos- 
phates. Human milk and that of herbivora is slightly alkaline and 
cow’s milk has been described as amphoteric, that is, it is alkaline to 
red litmus, acid to blue litmus. Vogel (10) states that he has never 
yet found perfectly freshly drawn cow’s milk to show a decidedly alka- 
