268 



Journal of Applied Microscopy. 



reached they were sealed in a flame. The method has been simplified by 

 Gruber and is easy of execution. Special test-tubes with a constriction below 

 the cotton plug may be obtained. After the medium is inoculated a vacuum is 

 produced in the tube, which is then sealed in the flame. If desired, colonies 

 can be obtained by making a so-called " roll-tube culture " after sealing the tube. 



ABSORPTION OF OXYGEN. 



If a solution of pyrogallic acid is rendered alkaline, it will immediately 

 become dark, then brown, and finally black, due to rapid absorption of oxygen. 

 This reaction has been utilized in a variety of methods. Buchner's method con- 

 sists in placing the inoculated tube inside of a larger one which contains on the 

 bottom some pyrogallic acid. Caustic alkali is added to the acid, and the tube 

 is then closed at once with a rubber stopper. 



DISPLACEMENT OF AIR. 

 This can be accomplished by passing through the tube or apparatus a 

 current of an inert gas. Hydrogen is usually employed for this purpose. The 

 Liborius tube is to be mentioned in this connection. After the medium is 

 inoculated a current of hydrogen is passed into the tube, through the side tube, 

 until the air has been displaced. When this result is attained, the tube is sealed 

 below the cotton plug, and finally the side-tube is likewise sealed. Various 

 modifications of the original tube have been proposed, but although they 



render the method less expensive they do not 

 materially simplify the procedure. 



Fig. 1 shows an apparatus which was 

 originally employed by the author. It can 

 be constructed by any one, and is simple, 

 inexpensive, and will give excellent results. 

 Ordinary test-tubes are employed instead of 

 the expensive tubes of Liborius. Moreover, 

 a large number of tubes can be placed in one 

 apparatus. The directions for use as given in 

 connection with the author's special apparatus 

 are applicable to this bottle. The stop-cocks 

 serve to seal the apparatus. 



A great variety of apparatus has been 

 described for the purpose of obtaining colonies. Some of these, like Botkin's, 

 enable one to make use of the ordinary Petri dishes. More often, however, 

 they consist of a special dish such as that of Kitasato. 



CULTURES IN THE PRESENCE OF AIR. 



This method, from the nature of the organisms under consideration, would 

 seem to be impossible. Nevertheless, as the author has shown, good cultures 

 can be obtained without the use of any special apparatus, and these cultures are 

 made apparently with free access of air. When a tube of glucose agar is 

 liquefied and then allowed to solidify, a drop or two of water will separate out 

 on the surface of the agar. If a stab-culture is now made, for instance of 



Fig. 1. 



