ISOLATION AND PURE-CULTURE METHODS 



35 



placed in the beaker, which is filled with water at from 40°-42° C. ; 

 and this temperature, which is above the point of solidification of 

 agar, should be maintained throughout the period of culture by the 

 addition of hot water when necessary. 



The method. In making the cultures the procedure may be as 

 follows : Some of the spores or bits of the material from which 

 cultures are desired are diffused in a drop of sterile water placed 

 in one of the short test tubes (or a flamed slide will suffice). The 

 three tubes in the beaker are denoted 1,2, and 3 respectively, and 

 may be so marked with a wax pencil. The short tube containing 

 the spores and tube No. 1 are taken between the thumb and index 



foe 



*•>*% 



%"• 



Fig. 8. Two Dishes from an Isolation Series of a Parasitic Fungus 

 (Photograph by Geo. F. Atkinson) 



finger and the index and middle fingers respectively, and held 

 almost horizontal, palm upward, the plugs having been previously 

 removed and held between the spaces of the remaining fingers. 

 The flamed but cold platinum needle, provided with a loop at the 

 tip, is taken in the right hand, dipped into the drop of spores, and 

 then into the agar of No. 1 and mixed. This may be repeated 

 several times, unless the spores in the drop are very numerous. 

 No. 1 is now placed in the former position of the short tube, and 

 No. 2 in the place of No. 1. The process is repeated with this 

 combination, and, finally, with Nos. 2 and 3 ; the contents of each 

 tube is then poured into a corresponding Petri dish upon the top 

 of which number, date, and any description desired may be in- 

 scribed with the wax pencil. 



