GELATIN 31 



9. Counterpoise and restore any loss by evaporation 

 with distilled water. 



10. Filter while boiling hot through plaited filter paper 

 just previously washed with 1/2 liter of boiling water. 



11. Pass the filtrate through the same paper till it is 

 bright and clear. 



12. Fill thirty sterile test tubes, using approximately 

 8 c.c. of this medium for each tube. Put the remaining 

 broth in a large, sterile flask. 



13. Heat the test tubes and contents in flowing steam 

 twenty minutes on three successive days. 



14. To sterilize a large flask of broth, heat for twenty 

 minutes four days in succession. 



GELATIN 



Gelatin is one of the tools of the microbiologist. As 

 such, it serves two purposes: as a solid culture medium, a 

 technical device by which the isolation of a single species 

 of microorganism is made possible, and, to those organisms 

 which secrete proteolytic enzymes, it serves as a nitrogenous 

 food material. 



Gelatin bears the distinction of being the first substance 

 used for a solid culture medium. This medium was origi- 

 nated in 1882 by Robert Koch and has since revolutionized 

 the science of microbiology. Prior to the introduction of 

 solid media, the isolation of a single species of microorganism 

 involved much difficulty and almost always a certain measure 

 of uncertainty. To quote from Jordan: " It cannot be a 

 mere coincidence that the great discoveries in bacteriology 

 followed fast on the heels of this important technical 

 improvement, and it is perhaps not too much to claim that 

 the rise of bacteriology from a congeries of incomplete 

 although important observations into the position of a 

 modern biologic science should be dated from about this 

 period (1882)." 



Koch's first plates were made by pouring the liquefied 



