540 Typhoid Fever 



of either with certainty, and until some satisfactory method 

 for their differentiation is found, the only solution of the 

 problem will be to transfer a large number of colonies to 

 some culture medium, in which specific differences can be 

 recognized, and study the resulting growths. 



Special media devised for the purpose of developing the 

 specific differences, such as rapidity of growth, acid-pro- 

 duction, etc., are numerous. Thus, Eisner* has suggested 

 the employment of a special medium made as follows: i 

 kilogram of grated potatoes (the small red German potatoes 

 are best) is permitted to macerate over night in i liter of 

 water. The juice is carefully pressed out, and filtered cold to 

 get rid of as much starch as possible. The nitrate is boiled 

 and again filtered. The next step is a neutralization, for 

 which Eisner used litmus as an indicator, and added 2.5-3 c - c - 

 of a ^ normal sodium hydrate solution to each 10 c.c. 

 of the juice. Abbott prefers to use phenolphthalein as an 

 indicator. The final reaction should be slightly acid. Ten 

 per cent, of gelatin (no peptone or sodium chlorid) is dis- 

 solved in the solution, which is boiled, and must then be 

 again neutralized to the same point as before. After filtra- 

 tion the medium receives the addition of i per cent, of 

 potassium iodid; then it is filled into tubes and sterilized 

 like the ordinary culture media. 



When water or feces suspected of containing the typhoid 

 bacillus are mixed in this medium and poured upon plates, 

 no bacteria develop well except the typhoid and colon 

 bacilli. 



These, however, differ markedly in appearance, for the 

 colon colonies appear of the usual size in twenty-four hours, 

 at which time the typhoid bacillus, if present, will have 

 produced no colonies discoverable by the microscope. 



It is only after forty-eight hours long after the colon 

 colonies have become conspicuous that little colonies of 

 the typhoid bacillus appear as finely granular, small, round, 

 shining, dew-like points, in marked contrast to their large, 

 coarsely granular predecessors. Unfortunately, many of 

 the small colonies that develop in Eisner's medium sub- 

 sequently prove to be those of the colon bacillus, and the 

 method is thus rendered unsatisfactory. 



Re"my f prefers to make an artificial medium approxi- 

 * "Zeitschrift fur Hygiene," xxn, Heft i, 1895; Dec. 6, 1896. 

 f "Ann. de 1'Inst. Pasteur," Aug., 1900. 



