ISOLATION OF BACTERIA IN PURE CULTURE 549 



to excise small bits of the agar plate inoculated with a bacterial 

 culture, and we obtain in this way a far better picture of the 

 actual morphology of the bacterium than by producing prepara- 

 tions according to the usual methods, whether it be the milder 

 procedure of emulsifying the bacteria in a drop of a staining 

 fluid, or one of the various staining methods with previous 

 fixation. 



If, owing to the minuteness or too crowded placing of the 

 microorganisms, we should fail in distinguishing what we de- 

 sired to see, such as for instance the cell division lines, by means 

 of the dry lens system, we need only place a coverglass on the 

 surface of the agar. Tliis will immediately adhere to the agar, 

 and, by means of the oil-immersion lens we shall be able to de- 

 tect the bacteria quite distinctly and also to trace, the growth 

 of a single element. 



Any one can readily be persuaded as to the faciUty with which 

 bacteria are distinguished on an agar surface without staining 

 or contrast, by examining an inoculated agar plate after a few 

 hours' incubation. 



REFERENCES 



Barber, M. A. 1908 The rate of multiplication of Bacillus coli at different 



temperatures. Jour, of Inf. Dis., 6,379. 

 BuRRi 1909 Das Tuschverfahren. Jena. 

 Hansen, Emil Chr. 1883-1888 Methode til Fremstilling af Renkulturer af 



Sacchaocjmaeter og lign. Mikrober. Medd. fra Carlsberg Lab. 



2, p. 152. 

 Hill, H. W. 1902 "Hanging Block" preparations for the microscopic obser- 

 vation of developing bacteria. Jour. Med. Research, 8, 202. 

 HoRT, E. 1920 The cultivation of aerobic bacteria from single cells. Jour. 



Hyg., 18, 361. 

 KtJSTER, ScHOUTEX 1921 Anlcitung zuT Kultur derMikroorganlsmen. Leipzig, 



p. 59. 

 Maloni:, L. H. 1919 A simple apparatus for isolating single organisms. Jour. 



Path, and Bact., 22, 222. 



