124 BAGTEBIOLOQY. 



a slanting position. With a platinum needle a bit of 

 the substance to be studied is smeared upon tube No. ] ; 

 without sterilizing the needle it is pa;ssed thoroughly 

 over the surface of the medium in tubes 2, 3, 4, etc., 

 etc., in succession. When development has occurred 

 essentially the same conditions as regards separation of 

 the colonies will be fqund as is the case when plates are 

 poured. If a slanted medium be employed, about the 

 most dependent angle of which water of condensation has 

 accumulated, as blood-serum, agar-agar, and potato, the 

 dilutions may be made in this fluid, and this is then to be 

 carefully smeared over the solid surface of the medium. 

 The tubes thus treated should be kept in an upright 

 position to prevent the fluid from flowing over the sur- 

 face. When sufficiently developed, single colonies may 

 be isolated from tubes prepared in this manner with 

 comparative ease. (See also method for the isolation 

 of bacillus diphtheria; on blood-serum.) 



