126 The Philippine Journal of Science 1913 



solution of the particular carbohydrate in distilled water, the 

 reaction would be reduced to its simplest terms. But the large 

 majority of microorganisms require proteid material in the 

 medium, which of course introduces another factor into the 

 equation and makes the reaction a resultant of two forces rather 

 than the effect of one. As was intimated, the use of media for 

 carbohydrates which require to be arranged in reaction is open 

 to objection. It is also objectionable to use solid media for the 

 reason that liquid media are more sensitive, and also because 

 upon the surface of solid media where free oxygen is at hand 

 many organisms will not ferment the carbohydrate in order to 

 get oxygen. This latter fact is made use of in the Russell 

 medium for identifying varieties of bacteria, but in finding out 

 how a given organism will react toward a given carbohydrate 

 the fluid media seem to be better. That our media should be 

 sterile need not be emphasized. That it often is not sterile after 

 three successive heatings for twenty minutes in the Arnold 

 sterilizer I have found such a common experience that I have 

 discontinued this method of sterilization of carbohydrates, and 

 now use only the autoclave. So far, I have not found that 

 heating for twenty minutes at 20 pounds' pressure has produced 

 changes in any of the carbohydrates, when prepared as described 

 below. After sterilization, the tubes are placed overnight in the 

 incubator; such as are not sterile are discarded next morning, 

 and the inoculations made as soon as possible. Were it not for 

 evaporation, the 37° incubator would be a far safer place for 

 storage of sterile media than is the ice box. It is probable that 

 some of the varying fermentative reactions given for the dys- 

 entery bacillus have been due to contaminative organisms, and 

 it might be added in passing that the only proper control of a 

 "crooked fermentation" is the actual plating out and reidentifica- 

 tion of the organism from the freshly isolated culture. 



The medium which has been found to give the most constant 

 results has been a peptone solution in distilled water — Witte's 

 peptone, 1 per cent; the desired carbohydrate (the purest obtain- 

 able), 1 per cent; sodium chloride, chemically pure, 0.5 per cent; 

 made up with distilled water. The medium is then distributed in 

 test tubes, 10 cubic centimeters in a tube, and is sterilized at 20 

 pounds' pressure for twenty minutes. Then to each tube is added 

 2 cubic centimenters of a 5 per cent filtered litmus solution which 

 has been autoclaved separately. This litmus solution is boiling 

 at the time introduced, and the tubes are then heated in the 

 Arnold sterilizer for fifteen minutes to ensure sterility. After 



