82 BAOTERIOLO&Y. 



level of the-ftuid. It is necessary to reduce the tempera- 

 ture of the mass to the point given, 68°-70° C, other- 

 wise the coagulation of the albumin will occur in lumps 

 and masses as soon as it is added, and its clearing action 

 will not be homogeneous. The process is a purely 

 mechanical one — the finer particles, which would other- 

 wise pass through the pores of the filter, being taken 

 up by the albumin as it coagulates and retained in the 

 coagula. 



At the end of one-half hour the boiling mass may be 

 easily and quickly filtered through a heavy, folded 

 paper filter at the room temperature, and, as a rule, the 

 filtrate is as clear and as transparent as agar-agar 

 usually appears. 



Another plan that insures complete solution of the 

 agar without causing the precipitates that are com- 

 monly seen when all the ingredients are added at 

 first and boiled for a long time, is to weigh out the 

 necessary amount of agar-agar, 10 or 15 grains, and 

 place this in 1300 or 1400 c.c. of water and boil down 

 over a free flame to 1000 c.c. The peptone, salt, and 

 beef-extract are then added and the boiling again con- 

 tinued until they are dissolved. The clarification with 

 egg albtimen may then be done, and usually the mass 

 filters quite clear and does not show the presence of 

 precipitates upon cooling. If the mixture is positively 

 alkaline, it is not only cloudy but it filters with diffi- 

 culty ; if it is acid, it is usually quite clear ; but, as 

 Schultz has pointed out, it loses at the same time some 

 of its gelatinizing properties. The bouillon should 

 always be neutralized before the agar-agar is added to 

 it, for if the bouillon be acid, from the acid of the meat, 

 it robs the agar, under the influence of heat, of some of 



