EXAMINATION OF MILK 155 



SECTION 3 



EXAMINATION OF MARKET MILK FOR TUBERCLE 

 BACILLI 



1. Secure a sample of milk and centrifugalize for 

 30 minutes at a speed of about 1,200 revolutions per 

 minute. 



2. Mix the sediment and the cream in a sterile tube; 

 if too thick add a sufficient amount of sterile o . 8 NaCl 

 solution. 



3. Make stains of the mixture for acid-proof bacilli. 



4. Divide the mixture into three parts and inject 

 subcutaneously into three guinea-pigs. 



Three weeks is about the shortest time in which 

 tuberculosis will develop. The guinea-pigs should be 

 watched closely after this time, and if any of them die, 

 postmortem examinations of the lesions should be 

 made and smears from the affected organs should be 

 stained to demonstrate the presence of tubercle bacilli. 

 Three guinea-pigs are used for an experiment of this 

 nature, because it is impossible to avoid injecting other 

 bacteria present in milk, which may cause the death 

 of one or more of the guinea-pigs before tuberculosis 

 has developed. 



SECTION 4 

 A STUDY OF THE ACID FERMENTATION OF MILK 



1. Secure three samples of milk, one of raw milk, 

 one of pasteurized milk, and one of certified milk. 



2. Divide each sample into three parts, and keep one 



