ESMARCH TUBES. 141 



as regards separation of the colonies will be found as 

 when plates are poured. If a slanted medium be em- 

 ployed, 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 flowing over the surface. When sufiiciently de- 

 veloped, single colonies may be isolated with compara- 

 tive ease from tubes prepared in this manner. (See also 

 method for the isolation of bacillus diphtherice on blood- 

 serum.) 



