NUTRIENT GELATIN. 63 



the bottom of the vessel from the direct action of the 

 flame by the interposition of several layers of wire gauze 

 or a thin sheet of asbestos-board. 



When the gelatin is completely melted, it may be 

 filtered through a folded paper filter on an ordinary 

 funnel ; if the solution is perfect, this should be very 

 quickly accomplished. 



The employment of the hot-water funnel, so often 

 recommended, has been dispensed with in this work 

 to a very large extent, as we know that, if the solution 

 of the gelatin is complete, filtration is so rapid as not 

 to necessitate the use of an apparatus for maintaining 

 the high temperature. The temperature at which the 

 hot-water funnel retains the gelatin is so high that evap- 

 oration and condensation rapidly occur, and in conse- 

 quence the filtration is, as a rule, retarded. The filtra- 

 tion is frequently done in the steam sterilizer, but this is 

 unnecessary if the gelatin is quite dissolved. At the 

 ordinary temperature of the room and by the means com- 

 monly employed for the filtration of other substances, 

 both gelatin and agar-agar may be rapidly filtered if 

 they are completely dissolved. 



It not infrequently occurs that, even under the most 

 careful treatment, the filtered gelatin is not perfectly 

 transparent (the condition in which it must exist, other- 

 wise it is useless), and clarification becomes necessary. 

 For this purpose the mass must be redissolved, and 

 when at a temperature between 60° C. and 70° C, the 

 whites of two eggs, which have been beaten up with 

 about 50 c.c. of water, are added. The whole is then 

 thoroughly mixed together and again brought to the 

 boiling-point, and kept at this point until coagulation of 

 the albumin occurs. It is better not to break up the 



