ITS CHEMICAL CONSTITUENTS. 339 



The ash of cows' milk contains, according to Weber's analysis, 

 conducted by Rose's method, 14'18-g- of chloride of potassium, 

 4'74-g- of chloride of sodium, and 23-46 of potash and 6'9G|} of soda 

 (combined with phosphoric, sulphuric, and carbonic acids). The 

 ash of ox-blood, on the other hand, after the abstraction of the 

 peroxide of iron, contains 38'82 of chloride of sodium, no chloride 

 of potassium, 29'09 of soda, and only 11'44-g- of potash. This 

 milk, therefore, independently of the absolutely small quantity of 

 salts, contains a relatively less amount of soda-compounds and 

 alkaline chlorides, but a much larger quantity of potassium- 

 compounds. In the ash of milk we moreover find, according to 

 Weber's analysis, 28'4^ of phosphoric acid, while in the ash of the 

 blood (according to the same analysis) there is only 7*74^ of this 

 acid, after deducting the iron. Finally, there is 17'34-g- of lime 

 and 2'20 of magnesia in the ash of the milk, while there is only 

 1'90-g- of lime and 0'75-g- of magnesia in the ash of the blood (after 

 a similar deduction of the peroxide of iron). Hence the milk 

 exhibits a considerable excess of phosphoric acid and earths over 

 the blood. The phosphoric acid present in the milk-ash is almost 

 wholly tribasic. We shall in a future part of the work see the 

 importance of these comparative numbers, in relation to the theory 

 of the secretions and the metamorphosis of matter generally. 



Alkaline carbonates are also present to some extent, if not in 

 all kinds of milk, at all events in cows' milk. Thus, when two 

 samples of fresh milk, one unmixed and the other treated with a 

 little acetic acid, be placed under the receiver of an air-pump, and 

 we produce a vacuum, the latter will be found to contain a much 

 larger quantity of gas, that is to say, of carbonic acid, than the former. 



Lactic acid is not contained in fresh milk, as we have already 

 shown in vol. i., p. 98, and it only appears to be formed 

 abnormally in the udders of graminivorous animals. The freshly 

 drawn milk of herbivorous animals always exhibits a slight alkaline 

 reaction, and is only rendered acid when the food of the animal 

 has been scanty and poor in quality. It still remains for us to 

 determine whether, in these cases, the acid reaction invariably 

 depends upon lactic acid, or, as may possibly be the case, on the 

 presence of acid phosphates, or even on butyric acid. The milk of 

 the bitch is, according to Bensch, neutral when the animal has been 

 kept on vegetable food ; whilst it is always acid when the food 

 has been exclusively animal. This acid reaction is most probably 

 owing to the acid phosphates, and more especially to super- 

 phosphate of lime. 



