BACTERIOLOGICAL ANALYSIS. 657 



General Considerations as to the Usefulness of the Sugar Tests 

 as applied to the Colon Bacilli. — The experience of observers who have 

 had most experience in the use of the sugar tests in the way I have 

 indicated tells in no uncertain voice in its favour ; but critics have 

 sprung up an 1 objected on more or less theoretical grounds against 

 its employment, without, I think, quite understanding the question. 

 They say — 



1. The reactions are not constant, and the number of 



varieties is too large, being in fact only limited by the 

 number of sugars used. 



2. The method is slow. 



1. The first objection is mainly based on such theoretical work 

 as has been done by Klotz, Twort, Penfold and myself, which 

 undoubtedly goes to show that the fermentative properties of an 

 organism are not constant hard and fast attributes, that, in fact, 

 one can educate organisms and increase their capacity for fermenting 

 carbohydrates. Working with cultures of typhoid it is quite easy 

 to produce several different strains from the same original culture, 

 strains that will ferment new sugars according to their education, 

 which shortly consists in growing them for longer or shorter periods 

 in such sugars. But, firstly, opportunity for these variations do 

 not seem very likely to occur in nature, and in the most important 

 cases they do not occur on points vital to the identification of these 

 types. It seems quite certain that if we place two identical orga- 

 nisms in identical conditions , say upon five sugars, we will get the 

 same results. If the reactions are different the organism is different. 

 Whether or not the difference is permanent or great can be arrived 

 at by more extended tests. It is only as we would expect amongst 

 so pleomorphic a group as are the bacteria, that we find intermediate 

 linking varieties between more stable types. The sugar reaction 

 should be taken as a whole, and their results considered along with 

 the data arrived at from other sources ; and although we cannot 

 rely too much on any hard and fast tabulated scheme of separation, 

 and although we must be prepared to find varieties of well known 

 organisms, yet it is obvious, I take it, that a rational use of the 

 "sugar" method, coupled when necessary with the other tests 

 indicated, has cleared the way amidst the maze of colon bacilli, 

 more than all the other work had since the first of the tribe was 

 discovered. 



2. As regards the time taken. After a little practice this is 

 very small, and it is in many cases virtually impossible to iden- 

 tify the organisms any other way, and, moreover, the time 

 actually occupied in working is small, and all the inoculating caaj-rTTjS^ 

 be done by a reliable assistant. ^\v^}}^Cj 



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