CH. v.] METHODS OF INOCULATION. 39 



altogether out of the tube and cotton-wool plug, and push 

 this latter down with the forceps into its former position. 

 Immediately after this proceed to inoculate the new culture- 

 tube by doing exactly the same as before, viz., draw up 

 slightly with the forceps the top part of its cotton-wool plug, 

 push through the remainder of this plug the pointed end of 

 the capillary pipette, i.e. the one containing the droplet of 

 the material to be sown, and push it into the material at the 

 bottom of the test-tube or flask. A trace of the sowing 

 material flows out by itself, or, if a large quantity is required, 

 it is carefully blown from the pipette, but, of course, not 

 so that the tube is emptied by the blowing. If the sowing 

 is to be carried out on the surface of solid material, the 

 seed is deposited on the surface ; if in the depth, the end of 

 the pipette is pushed down into the depth of the material 

 and the seed there deposited. The pipette is then altogether 

 withdrawn and the plug replaced as before. The new 

 tube is then placed in a beaker on a cushion of cotton-wool, 

 and exposed to the required temperature in the incubator. 



If we have, however, a culture-fluid or any fluid that con- 

 tains, as the microscopical examination proves, various species 

 of organisms, which we wish to isolate, then the method of 

 Klebs of "fractional cultivation," or the method of Lister 

 and v. Nageli of " dilution," or better still, Koch's method 

 of " plate-cultivation," is resorted to. 



The " fractional cultivation " consists in the attempt to 

 isolate by successive cultivations the different organisms that 

 have been growing previously in the same culture. If we 

 take up by means of a capillary pipette a trace of the culture- 

 fluid, and inoculate with traces of it in the manner above 

 described a series of new culture-tubes containing various 

 nourishing material, and expose these tubes in the incubator 

 to a definite temperature, say 35 C., then the chances are 



