MIL 
289 
the amount of phosphates can be determined separately by a plan 
which I communicated some years a jo to the British Association 
for the Advancement of Science. 
2. Albumen. — Rennet separates milk into curd and whey. 
When the operation has been properly conducted, a perfectly 
clear whev is obtained. On heating the clear and filtered whey 
nearly to the boiling: point of water, a flaky, curd-like substance 
separates itself. This substance is considered to be albumen. It 
exhibits all the distinguishing properties of the white of eggs, or 
albumen, but has not as yet been subjected to ultimate analysis. 
The albumen, or albuminous matter, which is not separated 
by rennet, but coagulates on boiling the whey from which the 
curd has previously been removed, amounts in cow's milk to from 
^ to per cent., or about ^ or i part of the casein. 
It is somewhat remarkable that this albuminous matter does 
not coagulate when new milk is simply raised to the boiling 
point of water. In this case a pellicle of oxydized casein is 
formed on the surface, but no albumen separates, and it thus 
appears that the curd of milk has first to be removed bv rennet 
before the albuminous matter can be obtained in a coagulated 
form. 
3. Sufjar of JMilli. — This variety' of sugar is solely obtained 
from the milk of mammalia. It is abundant in the milk of the 
herbivora, and only sparingly secreted by the carnivora. 
^lilk-sugar is contained in the clear whey from which curd 
and albumen have been removed by rennet and boiling, and is 
prepared in the following simple manner : — The clear whey is 
evaporated in shallow vessels until crystals begin to separate, 
then poured into the crystallizing pans, in which small pieces of 
wood are introduced, or strings are suspended, to act as nuclei 
for the deposit of the crystals of sugar of milk. In this wav it is 
obtained in long round sticks of a thickness of 2 or 2h inches in 
diameter, presenting {groups of right four-sided prisms, ter- 
minated by four-sided p^Tamids. The whey from which these 
crystallized masses have been removed, on further evaporation 
furnishes a second, less pure, smaller, j ellow-coloured crop of 
crystals. The purer variety is largely produced in Switzerland, 
where it forms an important article of commerce. 
Sugar of milk, or lactose, is less sweet to the taste than grape 
or cane sugar. It requires 5 to 6 parts of cold water for solution, 
dissolves readily in boiling water, and crystallizes again, on 
cooling, in white, semi-transparent, hard, small crystals, which 
feel gritty between the teeth. It is insoluble in alcohol and ether. 
In a pure state it may be kept unaltered for any length of 
time, being then insusceptible of fermentation. But if left in con- 
tact with casein and air, it gradually becomes changed either 
r 2 
