GENERAL CHEMISTRY OF MILK 99 



and the leukocytes are constantly breaking down, and it is pos- 

 sible that protein decomposition products may be formed which 

 are not found in normal milk. In the latter bacterial activity 

 may be responsible for the presence of decomposition products in 

 small quantity, since bacteria, chiefly hquefying micrococci, are 

 practically always present in the udder. Furthermore, the isola- 

 tion of proteins requires vigorous treatment, and consequently 

 traces of by-products may be present, and these are perhaps the 

 proteins referred to. 



Lecithin and Cephalin 



Both lecithin and cephalin are supposed to be present in milk, 

 although only in traces. They are waxy substances which are 

 soluble in alcohol and ether and contain P. and S. They are prob- 

 ably present in colloidal condition and are associated with the fat. 

 Reliable quantitative determinations are not available. 



Nitrogen-containing Extractives 



The presence of urea, creatin, creatinin, hypoxanthin, xan- 

 thin, and other similar substances in milk has been demonstrated. 

 Uric acid and hippuric acid are absent. 



Biscaro and Belloni have found an acid in milk which they 

 named orotic acid. This acid has never been isolated from any 

 other substance. The authors give the possibility of two formulae: 



/NH — CH2— CO /NH — CO — CH2 



C0< I or C0< J 



\nh — CO — CO \NH — CO — CO 



Milk-sugar 



The chief carbohydrate in milk is milk-sugar or lactose. Its 

 structural formula is as follows: 



CH2OH CHO 



HCOH HCOH 



D-dextrose HOCH HCH D-galactose 



HCOH HOCH 



HCOH HCOH 



in o CH 



Raudnitz states that there is but one carbohydrate — lactose 

 — in milk, and that the finding of other carbohydrates is due to 

 faulty technic. He argues that the findings are based on dif- 



