468 APPENDIX 



Differential Diagnosis of B. coli. The general characters of B. coli 

 will be found in the text of the present volume, but it may be stated 

 for diagnostic purposes that most reliance should be placed upon the 

 following characters. (But all characters must be taken into considera- 

 tion in forming an opinion.) B. coli produces a characteristic growth 

 on gelatine plate, smooth, milk-white colonies ; produces gas in 

 lactose, saccharose and glucose media ; is motile, non-liquefying (up 

 to the 14th day) and does not stain by Gram; produces acid 

 curdling of milk within four days at 37 C. The production of a 

 yellowish-green fluorescence in neutral-red agar shake culture and 

 the production of indol in peptone water or broth (but without 

 pellicle) are further tests relied upon by some. The Lawrence method 

 (State Board of Massachusetts) of testing for B. coli includes the follow- 

 ing seven tests : (a) characteristic appearance on agar streak, (//) growth 

 on litmus-lactose agar, (c) gas production in dextrose broth, (d) coagula- 

 tion of milk, (e) production of nitrites in nitrate broth, (/') production 

 of indol in Dunham's solution, and (g) non-liquefaction of gelatine.* 



B. lactis aerogenes is similar to B. coli, but coagulates milk much more 

 slowly and is non-motile. 



B. Gaertner and its allies ferment glucose but riot lactose in litmus 

 milk ; cultures are generally acid at first, and subsequently alkaline, and 

 there is no coagulation. 



B. typhosus produces no gas in any media, does not coagulate milk, 

 stains by Gram, and serum diagnosis is also practicable. 



Proteus group are similar to B. coli, except that they liquefy gelatine 

 and are slow in curdling milk. 



(c) B. typhOSUS may be examined for by adopting exactly the same 

 methods as for B. coli. Its detection in, and isolation from, water 

 supplies is so difficult as to be well-nigh impossible. The condition of 

 a water is, however, ascertainable short of an absolute test for B. typhosus, 

 valuable though that would be. 



(d) For the detection of the cholera spirillum, add 10 c.c. of peptone 

 solution (10 per cent, peptone, 20 per cent, gelatine, and 5 per cent, 

 salt) to 90 c.c. of the water to be tested. Incubate at 37 C. After 

 twelve to twenty-four hours incubation, examine loopfuls from the 

 surface pellicle for spirilla ; or plate out loopfuls of the pellicle on 

 gelatine and agar ; or test for cholera red reaction and Pfeiffer's reaction 

 and agglutination test ; or culture emulsion from Berkefeld filter in 

 peptone water, and then plate out on gelatine and agar from tubes 

 showing pellicle. 



(e) For the detection of StreptOCOCCi, plate out the emulsion obtained 

 from the Berkefeld filter on agar, and incubate at 37 C. After forty- 

 normal caustic soda until only faintly acid ; add white of egg ; sterilise and filter. 

 Before use add a gram of potassium iodide to every 100 c.c. Filter, and sterilise a 

 100 C. for twenty minutes on three successive days. Upon this acid medium 

 common water ibacteria will not grow, but B. typhosus and B. coli flourish the 

 former like "small clear droplets," the latter as dark brown globular masses. 



* Report of State Board of Health, Massachusetts, 1901, p. 400 ; ibid., 1902, pp. 262 

 and 280. 



