82 



PHARMACEUTICAL BACTERIOLOGY 



taken out of their natural environment and placed in artificial culture 

 media. It does not at all follow that, in the case of a mixed infection,, 

 the predominating and diagnostic microbe will remain the predominat- 

 ing t3T)e when said mixed infection is transferred to some artificial 

 culture medium. In fact, the predominating microbe may develop 



Pig. 31. — Manner of holding tubes when making subcultures. The cotton plugs, 

 removed from the two tubes, should be held in hand holding the platinum rod, as explained 

 in the text. (In this figure the cotton plugs are held in the hand holding the test 

 tubes, which is wrong.) (Williams.) 



very slowly or with great difficulty, if at all, in the artificial culture 

 media; whereas one or more of the associated microbes may thrive 

 remarkably well, soon entirely overshadowing the former. These and 



Fig. 32. — Making an E?march roll-tube culture. A lump of ice is placed in a dish 

 and the inoculated tube is placed horizontally in a groove in the ice and revolved until the 

 medium is well set. The groove may be made with test-tube full of hot water. (Williams.) 



other conditions occasion some of the great difficulties encountered in 

 determining the primary causes of some microbic and protozoic diseases 

 and infections. ' 



A. Test-tube Cultures. — Inoculate several test-tubes, containing 

 nutrient gelatin or agar gelatin, with any material which is known to 

 be bacterially infected. This is done by touching the infected material 



