MILK TESTING. 73 



percentage of fat of from 2 '5 to 3 per cent. As a result of the author's 

 own experience, he has found that the byre-test is only valuable where two 

 milkings per day are generally practised, and where the conditions of 

 milking in all the byres from which the milk is collected are essentially 

 similar, as is the case, for example, in many districts of Switzerland, 

 Austria, and the hilly districts of South Germany. As far as North Ger- 

 many and the middle districts of Germany are concerned, where the con- 

 ditions vary greatly in the different byres, it is absolutely worthless. 



For the detection of the less common adulterants of milk, such 

 as the presence of poisons, or the identification of bacteria, it is 

 obviously impossible in this work to give a more detailed descrip- 

 tion of the mode of investigation which must be adopted. 



In the case of the milk of single cows, the question as to whether 

 it is adulterated or not is a most difficult one to decide. With 

 market milk, however, which almost invariably represents the milk 

 of a number of cows, it is not so difficult; while in cases where the 

 milk of the larger herds is concerned, the detection of adulteration is 

 rendered much easier. The fixing of standards by which the purity 

 of milk should be determined is almost impossible. We shall, at 

 any rate, not attempt to lay down any limits of composition to which 

 the unadulterated milk of single cows is subject. Such figures would 

 not be of any assistance in forming a judgment. The following 

 figures which the author quotes, and which apply to market milk, 

 in which the variations found in the milk of single cows are 

 neutralized, are therefore to be used with very great caution. In 

 the majority of cases of German milk, produced under ordinary 

 conditions, the following figures may be taken as showing the 

 variations in its composition: 



Specific gravity at 15 C. a variation from 1*029 to 1*033. 



Fat, 2-50 per cent to 4 -50 per cent. 



Total solids, 10-50 ,,14-20 



Solids not fat, ... ... 8 ,, 10 



The specific gravity of the total solids should not exceed 1 '400. 



It must be strongly emphasized that the above figures, which 

 apply to market milk, must not, in any case, be held as applying 

 universally; but they may be found to hold fairly well in the 

 majority of cases. In different districts of Germany, however, they 

 must, in one or other of the particulars, be departed from. Also, it 



