Part II.] MILK LXSPECTIOX. 79 



sample of milk markedly deficient in any one of these qualities 

 cannot be fairly characterized as good, while a sample possess- 

 ing a good measure of all of them is fairly entitled to be called 

 good. 



Recognizing these qualities in the abstract is of little value to 

 the inspector unless they can be determined with regard to a 

 given sample of milk. Fortunately, the experience of the past 

 fifty 3^ears is also helpful at this point. 



Food Value. — There are three quite distinct aspects of the 

 question of food value of milk. Milk along with a few other 

 substances contains considerable amounts of substances called 

 vitamins, which are peculiarly important in the growth of the 

 infant. The presence of these vitamins makes possible the 

 healthy development of the child upon milk as the sole source 

 of food. As yet there is no available method of measuring the 

 amounts of these important vitamins present in any given 

 sample of milk, though they seem to be universally present in 

 all fresh milk. 



In the growing child not only must these vitamins be present, 

 but if muscles are to be formed the materials out of which 

 muscles are formed must also be at hand. Most important 

 among these materials are the nitrogenous elements commonly 

 called the proteids. The nitrogenous portions of milk are 

 known to be an especially desirable source of these proteids, 

 but the available knowledge concerning the transformation of 

 proteids into tissues does not yet offer simple and satisfactory 

 standards for expressing this aspect of the food value of milk. 

 The third and more general aspect of the food value of milk is 

 as a source of energy. The energy basis or the calorific l)asis is 

 the aspect of food value which can be readily and accurately 

 determined, though the determination is a somewhat technical 

 one. By suitable means it is possible to determine not only 

 the calorific value of milk as a whole, but also the value of 

 each of the component parts of the milk. Such studies have 

 shown that the calories in milk are not a fixed quantity, but 

 depend upon the chemical composition of the milk. A quart of 

 normal 3 per cent milk affords about 547 calories, while a 

 quart of 5 per cent milk yields about 775 calories. Fortunately, 

 for the purposes of .the inspector, the calorific value of normal 



