Lecture on Milk. 
411 
possess. Tlius, if au auimal takes castor-oil iu considerable quan- 
tities, the pui'gative effects of tlie oil pass into the milk. Coloui-ing 
matters — the red in madder, the blue in indigo, and the tint of the 
common weeds Mercurialis annua and Polygonum aviculare — likewise 
pass into milk and colom- it. In like manner smelling substances 
communicate a taste ; and it is thus that the tui-nip flavour is imparted 
to milk. 
The white appearance of milk is due to the milk-globtdes suspended 
in it. As these globules are separated in the shape of cream, the 
milk becomes clearer, and acquires a peculiar bluish tint, which is a 
very good indication of its character. The less transparent milk is, 
the better, and the more butter it contains. An extensive series of 
analyses of milk, which I have made, has brought out this fact, that, 
while the proportion of casein varies but in a trifling degree, the 
amount of butter or fatty matter in milk is subject to very great varia- 
tion. The following table will give some idea of the amount of 
Composition of New Milk. 
1. 
2. 
3. 
4. 
83'90 
85-20 
87-40 
89-95 
Butter 
7-62 
4-96 
3-43 
1*99 
3-31 
3-66 
3-12 
2-94 
4-46 
5-05 
5-12 
4-48 
•71 
1-13 
•93 
•64 
100-00 
100-00 
100-00 
100-00 
Percentage of dry matters . . 
16-10 
14-80 
12-60 
10-05 
these variations. In the first sample you have, in round numbers, no 
less than 7^ per cent, of butter ; in the second, 5 per cent. ; in the 
third, 3^ per cent. ; and in the fourth, 2 per cent. These four 
samples have been selected to show the widest range of variation 
which I have met with in milk. The fii-st sample, which is an 
exceedingly rich one, comes from the dairy of Mr. Harrison, of 
Froster Court ; the second sample is richer in butter than ordinary ; 
the third fairly represents the composition of milk of average good 
quality ; and the last, milk of poor quality. They are all four genuine 
milk, and not produced in any way abnormally. I ascribe the great 
richness of the first to the extremely good pastm-e upon which the 
cows were being fed at a season of the year when milk generally be- 
comes richer in quality, but less in quantity — that is, in September 
and October, and up to November. Generally speaking, milk is richer 
in the fall, and poorer in the spring ; but if animals are stinted in 
food in autumn, they yield not only little, but also poor milk. I will 
now point out the great difierences in the comj)osition of the milk of 
different animals. The following table shows the composition of 
the milk of herbivorous animals, and one example of the milk of 
carnivorous animals. 
