. SOUP POE CHILDEEX. 
159 
ounces of starcli. It is clear_, if we mix 12 ounces of steamed 
potatoes and 2^ ounces of pap made of pease_, we have : — 
Blood-forming’, Heat-producing substance. 
12 ounces Potatoes contain ... 0'250 (I) ... 2'50 (2^) 
2^ „ Pease „ ... OnOO (|) ... 1’25 (l|) 
14|^ ounces, containing 0750 (|) ... 375 (3|) 
or the proportion 1 : 5_, answering to the requirement of the 
boy. He will not only digest this mixture of 14J ounces of 
potatoes and pease more easily than the larger bulk of 24 
ounces of potatoes which nourished him imperfectly, but he 
will in this smaller weight of food receive one quarter more 
blood-forming nourishment ; a surplus necessary for the boy^s 
growth, that is to say requisite to increase the weight of his 
body. 
This may serve to exemplify the principles which have 
directed me in preparing a food for infants. Their correctness 
has been fully confirmed by the experience of many farmers, 
in their aim to produce milk and flesh. 
The composition of milk is not constant : its constituent 
parts (casein, butter, and sugar of milk) vary in their relative 
proportions, according to the food with which the individual 
has been nourished. 
According to the analysis of Haidlen, the milk of a healthy 
woman contains in one hundred parts 3T casein, 4*3 sugar of 
milk, and 3*4 parts of butter; it is generally poorer in casein 
than cow milk. If we admit that 10 parts of butter perform 
the same function in the animal body as 24 parts of starch 
(see Letters on Chemistry, p. 402) and 18 parts of sugar of 
milk as that of 16 starch, we may be able to compare, with 
some exactness, the nutritive value of milk with that of vege- 
table food (flour of wheat, &c.) by expressing the weight of 
butter and milk-sugar in milk by its equivalents in starch. 
We find, accordingly, that, — ■ 
Woman’s milk 
Cow’s milk, fresh 
Skimmed cow’s milk 
Wheat flour 
Proportion of blood-forming, 
contains 1 
Heat-producing matter. 
3*8 to 4-0 
3*0 
2-5 
5*0 
Woman^’s milk contains less salts than cow^s milk, but it 
possesses a stronger alkaline reaction, and contains more 
free alkali, which in milk is always potash. 
It is clear that we can easily calculate what mixture of cow^s 
milk and flour will contain the same proportion of blood and 
heat-producing ingredients as womaiTs milk (that is to 
say, the proportion I : 3*8), but in other respects it would 
