in the natural method ranking under the 4th 
order, gramina. The calyx is bivalvedand 
uuiilorous ; the corolla is very short ; the 
(stigmata pencil-like. There are 12 species, 
of which the most remarkable is the effusum, 
or common millet. 
MILK, is a liuid secreted by the female of 
all those animals denominated mammalia, and 
intended evidently for the nourishment of 
her offspring. 
The milk, of every animal has certain pe- 
; culiarities which distinguish it from every 
I other milk. But the animal whose milk is 
\ most made use of by man as an article of 
] food, and with which, consequently, we are 
] best acquainted, is the cow. Chemists, there- 
fore, have made choice of cow’s milk for 
their experiments. 
Milk is an opaque fluid, of a white colour, 
a slight peculiar smell, and a pleasant sweet- 
ish taste. When newly drawn from the cow, 
it has a taste very different from that which 
it acquires after it has been kept for some 
hours. 
It is liquid, and wets all those substances 
j which can be moistened in water ; but its 
consistence is greater than that of water, and 
I it is slightly unctuous. Like water, it freezes 
i when cooled down to about 30° ; but Par- 
i meatier and Deyeux, to whom we are in- 
debted for by far the completest account of 
l milk hitherto published, found that its freez- 
ing-point varies considerably in the milk ot 
different cows, apd even of the same cow at 
different times. Milk boils also when suf- 
ficiently heated ; but the same variation takes 
place in the boiling-point of different milks, 
though it never deviates very far from the 
boiling-point of water. Milk is specifically 
heavier than water, and lighter than blood ; 
but the precise degree cannot be ascertained, 
because almost every particular milk has a 
specific gravity peculiar to itself. 
When milk is allowed to remain for some 
time at rest, there collects on its surface a 
thick unctuous yellowish-coloured substance, 
known by the name of cream. The cream 
appears sooner on milk in summer than in 
winter, evidently owing to the difference ot 
temperature. In summer, about four days 
of repose are necessary before the whole ot 
the cream collects on the surface of the li- 
quid ; but in winter it requires at least double 
the time. 
After the cream is separated, the milk 
which remains is much thinner than before, 
and it lias a blueish-white colour. If it is heat- 
ed to the temperature of ICO 0 , and a little 
rennet (which is water digested with the 
inner coat of a calf’s stomach, and preserved 
with salt) is poured into it, coagulation en- 
sues; and if the coagulum is broken, the 
milk very soon separates into two substances ; 
a solid white part known by the name of 
curd, and a fluid part called whey. 
Thus we see that milk may be easily sepa- 
rated into three parts; namely, cream, curd, 
and whey. 
1. Cream is of a yellow colour, and its 
consistence increases gradually by exposure 
to the atmosphere. In three or four days 
it becomes so thick that the vessel which con- 
tains it may be inverted without risking any 
loss. In eight or ten days more, its surface 
is covered over with jnucors and byssi, and 
it has no longer the flavour of cream, but of 
very fat cheese. This is the process for mak- 
- 
MILK. 
ing what in this country is called a cream- 
cheese. 
Cream possesses many of the properties of 
an oil. It is specifically lighter than water ; 
it has an unctuous feel ; stains clothes precisely 
in the manner of oil ; and if it is kept fluid, 
it contracts at last a taste which is very analo- 
gous to the rancidity of oils. When kept 
boiling for some time, a little oil makes its 
appearance, and floats upon its surface. 
Cream is neither soluble in alcohol nor in oils. 
These properties are sufficient to shew us, 
that it contains a quantity of oil ; but this oil 
is combined with a part of the curd, and mix- 
ed with some serum; cream, then, is com- 
posed of a peculiar oil, curd, and serum. The 
oil may be easily obtained separate by agi- 
tating the cream for a considerable time. 
This process, known to every body, is called 
churning. After a certain time, the cream 
separates into two portions; one fluid, and 
resembling creamed milk; the other solid, 
and called butter. 
Butter is of a yellow colour, possesses the 
properties of an oil, and mixes readily with 
other oily bodies. When heated to the 
temperature of 96°, it melts, and becomes 
transparent; if it is kept for some time melt- 
ed, some curd and water, or whey, separates 
from it, and it assumes exactly tire appear- 
ance of oil. But this process deprives it in 
a great measure of its peculiar flavour. 
When butter is kept for a certain time, it 
becomes rancid, owing in a good measure to 
the presence of these foreign ingredients ; 
for if butter is well-washed, and a great por- 
tion of these matters separated, it does not 
become rancid nearly so soon as when it is 
not treated in this manner. It was formerly 
supposed that this rancidity was owing to the 
developement of a peculiar acid ; but Par- 
mentier and Deyeux have shewn that no acid 
is present in rancid butter. When butter is 
distilled, there comes over water an acid, 
and an oil, at first fluid, but afterwards con- 
crete. The carbonaceous residuum is but 
small. 
Butter may be obtained by agitating cream 
newly taken from milk, or even by agitating 
milk newly drawn from the cow ; but it is 
usual to allow cream to remain for some time 
before it is churned. Now cream, by stand- 
ing, acquires a sour taste; butter, therefore, 
is commonly made from sour cream. Fresh 
cream requires at least four times as much 
churning before it yields its butter, as sour 
cream does ; consequently cream acquires, 
by being kept for some time, new properties, 
in consequence of which it is more easily con- 
verted into butter. When very sour cream 
is churned, every one who lias paid the 
smallest attention roust have perceived, that 
the buttermilk, after the churning, is not 
nearly so sour as the cream had been. The 
butter, in all cases, is perfectly sweet; conse- 
quently the acid which had been evolved 
lias in a great measure disappeared during 
the process of churning. It has been ascer- 
tained, that cream may be churned, and but- 
ter obtained, though t'ne contact of atmo- 
spheric air should be excluded. On the 
other hand, it has been affirmed,, that when 
cream is churned in contact with air, it ab- 
' sorbs a considerable quantity of it. 
In all cases there is a considerable extri- 
cation of gas during the churning of butter. 
! From the phenomena, it can scarcely be 
I doubted that this gas is carbonic acid. Dr. 
Young affirms, that during the churning there 
is an increase of temperature amounting to 
four degrees. 
These facts shew that considerable chemi- 
cal changes go on during the process of 
churning. The agitation keeps the different 
substances in contact, and enables them to 
act upon each other. The expulsion oi car- 
bonic acid accounts for the diminution of 
acidity after churning; while the other phe- 
nomena would lead us to suppose that the 
cream, before it becomes butter, unites to a 
new portion of oxygen. 
The affinity of the oil of cream for the 
other ingredients is such, that it never sepa- 
rates completely from them. Not only are 
curd and whey always found in the cream, 
but some of this oil is constantly found in 
creamed milk and whey; for it has been as- 
certained by actual experiment, that butter 
may be obtained by churning whey. 27 
Scotch pints of whey yield at an average 
about a pound of butter. This accounts tor 
a fact well known to those who superintend 
dairies, that a good deal more butter may 
be obtained from the same quantity of milk, 
provided it is churned as drawn from the 
cow, than when tiie cream alone is collected 
nnd churned. 
The buttermilk, as Parmentier and Dey- 
eux ascertained by experiment, possesses- 
precisely the properties of milk deprived of 
cream. 
2. Curd, which may be separated from 
creamed milk by rennet, has many of the 
properties of coagulated albumen. It is 
white and solid ; and when all the moisture 
is squeezed out, it has a good deal of brittle- 
ness. It is insoluble in water ; but pure alka- 
lies and lime dissolve it retidily, especially 
when assisted by heat; and when fixed alkali 
is used, a great quantity of ammonia is emit- 
ted during the solution. The solution of 
curd in soda is of a red colour, at least if heat 
is employed ; owing probably to the separation 
of charcoal from tire curd by the action of 
the alkali. Indeed, when a strong heat has 
been used, charcoal precipitates as the so- 
lution cools. The matter dissolved by the 
alkali may be separated from it by means of 
an acid; but it has lost all the properties of 
curd. It is of a black colour, melts like tal- 
low by the application of heat, leaves oily 
stains on paper, and never acquires the con- 
sistence of curd. Hence it appears that 
curd, by the action of a fixed alkali, is de- 
composed, and converted into two new sub- 
stances; ammonia, and oil or rather fat. 
Curd is soluble also in acids. If, over curd 
newly precipitated from milk, and not dried, 
there are poured eight parts of water, contain- 
ing as much of any of the mineral acids as 
gives it a sensibly acid taste, the whole is 
dissolved after a little boiling. Acetic acid 
and lactic 'acid do not dissolve curd, when 
very much diluted; but these acids, wheiv 
concentrated, dissolve it readily, and in con- 
siderable quantity. It is remarkable enough, 
“hat concentrated vegetable acids dissolve 
curd readily, but have very little-, action on it 
when they are very much diluted ; whereas the 
mineral acids dissolve it when much diluted ; 
but when concentrated, have- either very little 
effect on it, as sulphuric acid, or decompose 
