METHOD FOR THE ISOL.\TION OF BACTERIA IN PURE 

 CULTURE FROM SINGLE CELLS AND PROCEDURE 

 FOR THE DIRECT TRACING OF BACTERIAL GROWTH 

 ON A SOLID MEDIUM 



J. 0RSKOV 

 Assistant Bacteriologist of the Slate Scrum Inslilutc, Denmark (Dr. Th. Madsen) 



Received for publication January 17, 1922 



By a pure culture we understand, as is well-known, a culture 

 consisting of individuals of which we know with certainty that 

 all are descended from one single cell, and from one only. As 

 all bacteriologic work, of whatever kind it may be, depends on 

 our working with such rehable pure cultures, many efforts 

 have, of course, been made in the course of time in order to 

 devise reliable methods of isolating a single bacterium. 



The first investigator who solved the problem in a satisfac- 

 tory way, — although not in regard to the bacteria proper — was 

 Emil Chr. Hansen. The principle of his method was, briefly 

 stated, to observe directly under the microscope the growth of 

 the individual yeast-ceU until it has formed a small colony in a 

 gelatin droplet on the lower surface of a coverglass in a moist 

 chamber. Yeast-cells are however far bigger than most bac- 

 teria, and there is no possibility of tracing with any certainty 

 the growth of a bacterium, as for instance a colon bacillus, in 

 a similar way in gelatin. 



Of methods that have been proposed and employed for single 

 cell cultivation of bacteria, the best known are those of Schouten, 

 Barber and Malone, none of which have however attained any 

 extensive application, no doubt partly owing to the intricate 

 apparatus they require, and partly to the difficulty involved 

 in picking up such minute objects as bacteria with such relatively 

 coarse implements as pipettes and loops; and when Barber states 

 that he is able to pick up successively each single one of four 



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THE JOURNAL OF BACTERIOLOOT, VOL. VII, NO. 6 



