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 condi- 

 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. 



