BACILLUS OF CHOLERA 139 



cells are very short motile rods, which increase in length 

 when grown artificially. Carbon dioxide and hydrogen are 

 liberated from a nutrient medium which contains no sulphur. 

 1 grm. of sulphur is decomposed in forty-eight hours in a 

 bouillon mixed with ammonium tartrate and with sulphur 

 in excess. 



Other bacteria, however, also generate sulphuretted hy- 

 drogen, to prove the presence of which it is only necessary 

 to hang strips of paper saturated with lead acetate in the 

 test-tubes containing the cultures, when a blackening of 

 the paper will be found with most water and air bacilli. 

 According to Mace this reaction becomes more distinct if 

 some flowers of sulphur be 

 added to the culture medium. 



Bacillus of Asiatic cholera, 

 and allied micro-organisms. 

 Koch discovered a comma- 

 bacillus in the evacuations 

 and the intestines of cholera 



patients, and adduced evi- FIG. 48. CHOLERA BACILLI, FROM A PURE 



CULTURE. (After Jaksch.) 



dence proving that this micro- 

 organism is the cause of the disease. He found it also in 

 the water of a tank in the neighbourhood of Calcutta. Ex- 

 periments have shown that the comma-bacilli can multiply 

 very well in sterilised water, whereas in ordinary water they 

 are soon overgrown by the water-bacteria ; and they can 

 tolerate just as little the concurrence of other bacteria, arid 

 consequently perish in decomposing liquids, although Gruber 

 has obtained pure cultures from alvine evacuations which 

 had been allowed to putrefy for a week. 



The pathogenesis of this bacillus has, however, recently 

 been rendered doubtful by the experiments (performed on 

 themselves) of Pettenkofer and Emmerich at Munich, 

 and Hasterlik in Vienna ; and of Dr. A. J. Wall, of H.M. 



