122 BACTERIOLOGICAL ANALYSIS LESSON 



(3) Now keep them at 38*5 C. for several days. 

 There will be no smell. 



Examine the contents of the tubes microscopically, 

 and make plates. 



The latter should remain sterile. 



B. HOW TO EXAMINE A SAMPLE OF UNSOUND MEAT. 1 



(1) Feed mice or rats with portions of it, and watch the 

 effect. 



If they die, make plate cultures from the organs and 

 heart's blood (vide p. 42). 



(2) Make an extract in sterile broth or saline solution of 

 the sample supplied, and inoculate mice or other animals 

 subcutaneously. 



If they die, make plate cultures as before, and separate 

 the organisms obtained. 



(3) Prepare an extract as above, and make plate cultures 

 in the ordinary way, and also roll tubes. 



Keep the former aerobically, the latter anaerobically. 

 Separate the various organisms as they appear. 



In all cases, the organisms which are separated should 

 be examined as to their virulence, both by means 

 of feeding experiments and by inoculations. 



In cases of food poisoning, it has been shown that at 

 times organisms may kill if taken in by the mouth, 

 while they fail to do so if injected subcutaneously. 



For separation of ptomaines and toxines vide p. 172. 



1 These experiments can only be performed under a licence and a 

 special certificate. 



