BACTERIA OF MILK 



79 



2. ]\Iake plates on gelatin each hour 

 up to twelve hours after the milk was 

 drawn. 



3. Determine the increase or decrease 

 of bacteria as indicated by the number 

 of colonies on the plates. 



Exercise 115. The Catalase of Milk 



]\lilk catalase is an enzyme which 

 arises in part from the leucocytes, but 

 in large part from the microorganisms, 

 of the milk. This enzyme may be demon- 

 strated by its ability to liberate oxygen 

 from hydrogen peroxide, by an action 

 which may be represented by the follow- 

 ing formula : 



2 HP, = 2 HP + 0,. 



The value of the test is, according to 

 Gerber, (a) to determine the health of 

 the animals, (5) to reveal inflammation 

 of the udder, (c) to detect abnormal 

 milk, ((Z) to determine the age of milk 

 and the relative number of bacteria pres- 

 ent, (e) to detect colostrum. 



Barthel. Jlethoden zur Untersuchung von Milch 



und Molkereiprodukten, 2te Aufl. Leipzig, 1911. 

 Jensen. Centralbl. f. Bakt., 2te Aht., 18 : 211. 



1906. 

 LoBECK. Molkerei-Zeitung, Hildesheim, Xr. 5, 



1910. 

 KnssELi.. Bulletin No. 18, Wisconsin Agr. Exp. 



Sta., 1889. 

 Weigmann. Mykologieder Milch. Leipzig, 1911. 



1. The student may use the Gerber- 

 Lobeck Reductase apparatus (Fig. 33) 

 or the simple arrangement of test tubes 

 shown in Fig. 34. 



Fig. 33. Gerber-Lobeck 

 Eeductase apparatus 



1, flask ; 2, gas-measuringtube ; 

 3, stopper; a, perforation to 

 allow escape of air compressed 

 by insertion of tbe stopper ; b, 

 narrow tube through which 

 evolved gases rise and dis- 

 place water through the open- 

 ings, c, and allow it to rise in 

 outer chamber ; d, scale show- 

 ing amount of gas evolved 



