498 



SUMMARY OP CURRENT RESEARCHES RELATING TO 



cover, and if, instead of water, some nutrient medium be used, anaerobic 

 bacteria can be developed in the cliamber. 



For test-tube cultivations, after the glass has been washed outside with 

 a 2 per cent, sublimate solution, it is scratched round at the level of 

 the gelatin with a file and then broken off. From the gelatin a colony 

 is dug out with a sterilized knife, and treated as above. 



In this way tube cultivations become accessible to the Microscope and 

 to photomicrography. Agar cultivations may be treated in a similar 

 manner, but stronger heating is required. A mixture, however, of equal 

 parts of meat-peptone-gelatin and agar-meat-peptone produces a mass 

 which is fluid at 48" C. and can be preserved at 28° 0. 



Modification of Koch's Plate Method.* — Dr. E. J. Petri recommends 

 flat double vessels of 10-11 cm. in diameter, and 1-1 '5 cm. in height. 

 The one used as the cover, of course, is a little larger. The gelatin, pre- 

 pared in the usual manner, is poured in so as to form a layer of only a few 

 millimetres thick, and then the cover imposed. A level layer is easily 

 obtained by gentle to and fro movement. Except the edge, every part of 

 the gelatin is accessible to the Microscope. The gelatin dries very slowly, 

 and may be kept damp for a long time by putting several of these small 



vessels within a large one, with a piece of 

 Fia. 146. damp filter paper, and then covering with 



f - I a bell-jar. These vessels answer very 



11 well for agar plates. Numbering the 



\ colonies is very simple. The cover is 



replaced by a glass plate marked out in 

 divisions, through which the position and 

 number of the colonies are noted. 



Method for Cultivating^ Anaerobic 

 Bacteria.| — Dr. M. Gruber uses a tube 

 made of easily fusible glass ; it is about 

 Fig. 147. 25 cm. in length, and the wider part about 

 2 cm. in diameter. The neck, about 5 cm. 

 long, is only 3-4 mm. wide (fig. 146). 

 After having been plugged with cotton 

 J \ j \ wool and sterilized in the usual manner, 



/ \ (^ ^•l *^^ lower part or body receives 10-12 cm. 



of gelatin, introduced with the usual pre- 

 caution, and is then again sterilized 

 at 100°. 



After having been inoculated by the 

 aid of a platinum wire, the cotton-wool 

 plug is rammed down tightly and a 

 caoutchouc plug, with a piece of rect- 

 angular glass piping, is fitted into the 

 head. The glass piping is connected with 

 an air-pump, and the air exhausted as far 

 as possible ; the I'esidual air is removed 

 by immersing the tube in water at 30°-35°, 



and boiling. The contents of the tube are 



prevented from bubbling uj) by gently 

 heating tlic junction of the neck and body with a Biinscn's burner. The 

 evacuation and boiling occupy about a quarter of an hour. 



* Ccntralbl. f. Cactcriol. u. rarasitenk., i. (18S7) )ip. 27K-80. 

 t Ibid., pp. 307-72 (2 fi^.s.). 



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V. J 



