GENERAL CONSIDERATIONS 5 



isolated from normal stools of healthy persons. Of these 8 did 

 not ferment lactose although they fermented glucose. Of the 

 remaining 93, 72 were completely positive as regards fermenta- 

 tion of glucose and lactose, positive neutral red reaction, pro- 

 duction of indol, acid and clot in litmus milk and reduction of 

 nitrates, 12 were non-motile, otherwise typical, 2 produced no 

 indol as their only abnormality, 2 failed to give the neutral red 

 reaction, 4 were typical except that they did not clot milk. 

 That is leaving out motility as a distinguishing character 

 84 per cent, were completely positive in their characters. 



Of these organisms about half fermented dulcite while 

 considerably less than half fermented saccharose. 



Houston 1 obtained very similar results with 60 B. coli 

 organisms isolated from fresh cow-dung. 95 per cent, gave 

 acid or clot in milk, 967 per cent, gave indol, 967 per cent, 

 acid and gas in lactose media, 98-3 per cent, a positive neutral 

 red reaction. 



53 out of the 60 (88 per cent.) were quite typical as regards 

 all these tests. 



MacConkey 2 records the examination of 178 samples of 

 human faeces and 131 samples of animal excreta, derived from 

 the horse, calf, goat and pig. Ignoring for the moment most of 

 the sugar-alcohol tests which were also employed, and excluding 

 a few yellow liquefying organisms certainly not members of the 

 group the results obtained may be tabulated as follows : 



Strains isolated Percentages 



Human Animal Human Animal 



Milk clotted ... ... 178 126 100 100 



Indol formed 164 122 92 96*8 



Gelatine not liquefied... 175 124 98*2 98*4 



Saccharose fermented 76 56 42 44*4 



,, not fermented 103 70 58 55^6 



All the organisms fermented both glucose and lactose. 



MacConkey strongly advocates the use of fermentation tests 

 including lactose, saccharose, dulcite, adonite, inulin, inosit and 

 mannite, and the abandonment of many of the old tests. In 



* Ibid. 1904-5, p. 358. 



2 Journ. of Hygiene, 1909, IX, p. 86. 



