26 Milk and Its Products 
chloride of potash is largely in excess of the 
chloride of soda. This is exactly opposite to the 
proportions of these two salts in the blood. 
Other constituents.— Besides the. constituents enu- 
merated above, several other compounds are more or 
less normally present in milk in minute quan- 
tities. 
A small amount of citric acid is said to be a 
normal constituent of milk. 
A peculiar substance called lactochrome is also 
a normal constituent of milk, and gives to it its 
characteristic color. This has been already men- 
tioned in connection with the palmitin. The amount 
of lactochrome present varies under many coundi- 
tions, notably the breed of the animal and .the 
character of the food. Whatever other conditions 
may prevail, the milk is always‘of a higher color 
where the animals are fed on fresh green forage. 
This has led to the idea that the color of, the 
milk is in some way connected with the condition 
of the chlorophyl or green coloring matter of the 
plant. Careno* has suggested that as the chloro- 
phyl undergoes a change when the plant is dried, 
the digestive organs of the animal will have a 
different effect upon it, and so account for the 
difference in color in the milk. 
An albuminoid called lactoprotein has also been 
described in milk. 
Urea to the extent of .001 of 1 per cent may 
also be regarded as a normal constituent of milk. 
*Milch Zeitung, vol. xxiv. 387. 
