ISOLATION OF ANAEROBES 459 



not necessary for photographic work, as sections for that purpose 

 may be cut from tubes of agar and may then be mounted between 

 cover and sHde. Fehrs and Sachs-Mticke used a similar method, 

 covering the agar with a photographic plate, Krumwiede and 

 Pratt used Marino's method satisfactorily for the isolation of fusi- 

 form bacilli, sealing the open crack with wax. Rhein used it with 

 satisfaction for general anaerobic work, pouring a sterile agar layer 

 on either side of the inoculated one. Dick used the method of 

 Rhein, replacing the top dish by a layer of paraffin. All these 

 methods are probably preferable to surface plating for isolation 

 purposes, but are somewhat cumbersome. 



Foth complains that the invention of new anaerobic methods 

 has become a sort of sport. Many procedures are too complicated 

 to use, though most methods will serve well for the cultivation of 

 anaerobes. It would seem as though any method employing 

 sticky black pyrogallic acid and alkali should be avoided, or at 

 least only chosen in the modification of Lentz. 



Certain workers with surface methods have charged that deep 

 colony procedures do not give pure cultures. Either type of pro- 

 cedure will give pure cultures in the hands of the critical worker 

 and impure ones in the hands of the uncritical one. But I have 

 found in making a large collection of anaerobes that the cultures 

 from laboratories whose isolation procedure was a deep colony 

 method were more often pure than those from laboratories where 

 surface methods were preferred, and I believe that, with the same 

 amount of labor, the same expenditure of time and material, and 

 the same degree of critique, the deep-colony methods are more 

 successful than are surface ones. 



Deep-colony methods have been described by the Hesses, 

 by Liborius, and by Veillon and Zuber, and they have been 

 used extensively by von Hibler, Burri, and by French workers. 

 Von Hibler (1908) preferred deep colony isolation to plate methods 

 because of the fact that water of condensation was likely to render 

 plates worthless. 



The selection of a suitable medium for deep-colony isolation is 

 an essential to its success. For general work the primary require- 

 ment is that the nutriment in the medium allow every anaerobe 



