588 BACTERIOLOGY.. 



10. Then try indol reacton with the same tubes. 



11. While these tubes are incubating use material 

 from the suspected colonies on the plates (1 and 5) for 

 hanging drop cultures. 



12. Meanwhile make stained cover-glass prepara- 

 tions from other colonies of suspected cholera on the 

 plates (1 and 5). 



13. Make gelatin tube cultures from colonies on 

 plates (1 and 5). 



14. Make gelatin tube cultures daily for five or six 

 days, to study shape of growth along the line of punc- 

 ture to preserve the culture. 



B. Suspected water. 



Add to 500 c.c. or 1 litre of the water to be exam- 

 ined in a flask half -full enough peptone-salt solution 

 (20 per cent, peptone and 10 per cent. NaCl) to make 

 a 1 per cent, solution of peptone. Then proceed as in A. 



PFEIFFER'S SERUM REACTION. All authors now 

 agree that the differentiation of the cholera vibrio from 

 other similar vibrios cannot always be made by the cul- 

 tural method, nor is the usual inoculation of animals 

 sufficient. For this purpose serum is employed either 

 by making intraperitoneal injections of a surely fatal 

 dose of the suspected spirillum along with the serum 

 of animals immunized to undoubted cholera cultures, 

 or by watching the action of the spirillum in the hang- 

 ing drop when added to a dilution of the above men- 

 tioned serum, so as to note whether immobilization 

 and clumping occurred. 



