; &NJ5. YHE PUBLIC HEALTH 



CHAP. 



Ash derived from 

 the following salts, of 

 which the percentage 

 composition according 

 to Soldner 



Water 



7-20 



"Besides the above there are the colouring-matter of milk (lactochrome), 

 odorous principles, bitter principles (probably derived from the plants 

 eaten), small quantities of other proteid bodies, kreatinine, urea, alcohol, 

 and fluorides." 



In addition milk contains a number of enzymes or ferments, 

 which are of considerable interest. The following may be 

 mentioned : 



G-alactase. This is the principal proteolytic ferment found 

 in milk. It converts proteids into proteoses and peptones, 

 and finally into amino-acids. It was first recognised by 

 Babcock and Eussell in 1897. According to Jensen it 

 liquefies gelatine. Later investigations have shown that 

 galactase is probably a mixture of enzymes. 



Spolverini found trypsin and pepsin in milk, but this 

 observation has not been confirmed. 



Lipase. This fat-splitting ferment has been found by a 

 number of observers. It hydrolyses butyrin into glycerine 

 and butyric acid. 



Catcdase. The ferments included under this name have 

 the power of decomposing hydrogen peroxide and are found in 

 milk. Peroxidases are also present, shown by their power of 

 effecting the oxidation of certain easily oxidisable substances. 



Eeductases. Apparently reducing ferments are present in 

 milk. Formalin-methylene blue solution is reduced by fresh 

 milk, and this is supposed to be due to a reducing ferment. 



Little or nothing is known about the physiological im- 

 portance of these enzymes. Their thermal death points vary 

 with the different ferments, but all those in milk lie between 



