176 



BACTERIOLOGICAL METHODS 



and toxin-bearing meats from which it has taken up the poisons 

 by absorption. It is therefore desirable and often necessary 

 to supplement the bacterial count by the toxicity test. 



The numerical limit above suggested (1,000,000 per gram 

 of the meat substance) pertains to bacteria found upon the ex- 

 terior of the meat bulk or in the outside cells and tissues of the 

 meat bulk or meat particles. Proper care must therefore be 



observed in taking samples 

 and in preparing the sample 

 for plating. In the case of 

 bulk meats such as whole 

 slaughtered animals, hams, 

 bacon, etc., pieces as nearly 

 cubical as possible (about i 

 gram each) are removed with 

 a sharp sterilized scalpel, 

 the outer surface of the meat 

 forming one face of the cube. 

 This is to be weighed and 

 pulped in a sterile mortar 

 with an equal amount of 



sterile normal salt solution 

 Fig. 58. — Illustrating the method of j ^v." 1 ^ f ' 1 " 



making an intravenous injection into a and ttUS pulped material IS 

 rabbit. The ear is manipulated to induce ^-^^^ ^^^^^ ^p ^Yie desired 



hypersemia and the surface vein is com- _ _ '^ _ 



pressed near the base of the ear, to facilitate dilutions for plating, USing 



SUXif "' **= ''"'''' """"^ normal salt solution. Gela- 



tin media should be used for 

 culturing and incubation should be done at 20° C. for a period of 

 3 days and the counts made. In the case of sausage meats and 

 comminuted meats generally, take i gram quantities, pulp 

 thoroughly and mix thoroughly with the required amount of nor- 

 mal saline and plate. In the case of soups and soup stocks hav- 

 ing a meat or meat derivative base, take i cc. quantities, from 

 the thoroughly mixed sample, dilute and plate. 



