44 KANSAS UNIVERSITY SCIENCE BULLETIN. 



After filling, the pipette is caused to descend and the culture 

 drop brought into the field. The tip of the pipette, which 

 meanwhile is kept in view, is raised until it comes into con- 

 tact with the micro-organism to be isolated. This immedi- 

 ately enters the pipette by means of capillarity, often in com- 

 pany with other cells ; though I have often succeeded in 

 withdrawing the pipette quickly enough to secure only the 

 cell desired. After securing the cells, the cover is moved 

 by means of the mechanical stage until the tip of the pipette 

 can be brought into contact with an unoccupied part of the 

 cover, where its contents are discharged. The discharge is 

 accomplished by blowing gently into a rubber tube, t, one 

 end of which is attached to the outer end of the pipette 

 while the other is held in the mouth of the observer. Should 

 there be other cells with the one selected, I usually make 

 a series of droplets with the contents of the pipette, in one 

 of which the cell desired appears alone or with so few other 

 cells that isolation is generally easy at a second attempt. 

 When motile organisms are to be isolated I often place a 

 sterile drop beside the culture drop in such a position that 

 the two drops are in contact at a portion of their circumfer 

 ence. The more active bacteria will soon move into the new 

 drop where they may be taken up by the pipette. 



Once isolated, the micro-organism may be picked up and 

 carried to any part of the cover, or, if desired, a fresh sterile 

 cover may be placed on the box and the single cell deposited on 

 it, or, finally, it may be received into a drop on a platinum loop 

 and transferred to a test-tube. In my work I have usually 

 left the isolated cells on the same cover and kept them in view 

 during their development, but in some cases I have drawn 

 the isolated cell well back into the pipette, sealed both ends 

 of the pipette, and placed it in the incubator for development. 

 Many isolations may be made on the surface of one large 

 cover. No difficulty is experienced from the running together 

 of droplets if, just before sterilizing, the cover is rubbed with 

 a piece of chamois skin, or with a cloth having the least trace 

 of vaseline on it. Care must be taken in sterilizing not to 

 leave the cover in the flame long enough to burn off all the 

 vaseline. 



