and Laboratory Methods. 



1755 



Nikirforoff introduced a method by which anaerobes can be cultivated in a 

 hanging drop. 



Alethod. — Use a sUde which carries a ground glass ring, just as for making 

 an ordinary hanging drop preparation. Cover the ground edge of the ring which is 

 used for the support of the cover glass with vaseline. Place the cover glass with the 

 hanging drop on the ring, so that one side of the ring is not covered. Insert 

 here a small drop of pyrogallic acid. Move the cover glass into its proper place, 

 that is, so that it covers the ring completely. The drop of pyrogallol now 

 spreads over the whole periphery between the cover glass and 

 ring. Now carefully move the cover glass in the opposite direc- 

 tion and put a drop of potassium hydroxid upon the thus un- 

 covered part of the ring. Replace the cover glass and make it 

 fast. The two drops will mix and the absorption of oxygen takes 

 place. Instead of applying the alkaline pyrogallol on the surface 

 of the ring, it may be put on the bottom of the object carrier in 

 the center of the ring. Later, Nikirforoff and Braatz devised 

 special object carriers in which the hanging drop may be examined 

 in a hydrogen atmosphere. 



Salomonson (1889) suggests the use of aerobic bacteria as the 

 agents for the absorption of oxygen. He uses two test tubes 

 (Fig. 36). The smaller inner tube (a) contains the culture 

 medium inoculated with the anaerobic species. The larger outer 

 tube (b) with constricted neck and cotton plug holds a bouillon 

 culture of one or more strictly aerobic species. As soon as both 

 tubes are inoculated with their respective organisms the outer 

 tube (b) is sealed at (c). 



Besides the various apparatus described in this category, most 

 of the apparatus for plate cultures referred to under Classes I and 

 II may also be used for the pyrogallol method. 



IV. 



Fig. 36. 



REDUCTION OF OXYGEN. 



In order to simplify apparatus and manipulation used for cultivating anaero- 

 bic bacteria, and to be able to make cultures of anaerobes in the presence of air, 

 attempts were made to reduce the oxygen in the medium. Various agents have 

 been used to accomplish this end. 



A. Mixed cultures. 



One of the simplest though not altogether satisfactory ways to cultivate anae- 

 robes under aerobic conditions is that of making mixed cultures, i. e., the culture 

 medium containing the anaerobic species sought for is inoculated with one or 

 more strictly aerobic species. While many investigators have used this method 

 successfully, there seems to exist some controversy regarding the specific role 

 which the aerobes play in preparing favorable conditions for the anaerobes in 

 mixed cultures. Pasteur holds that the aerobic bacteria are capable of using up 



