XX. THE STUDY OF THE PATHOGENIC 

 BACTERIA. 



The student, who has conscientiously worked out the 

 methods, etc., previously dealt with, is in a position to 

 make accurate observations and to write precise de- 

 scriptions of the results of such observations. He is, 

 therefore, now entrusted with pure cultivations of the 

 various pathogenic bacteria, in order that he may 

 study the life-history of each and record the results 

 of his own observations to be subsequently corrected 

 or amplified by the demonstrator. In this way he is 

 rendered independent of text-book descriptions, the 

 statements in which he is otherwise too liable to take 

 for granted, without personally attempting to verify 

 their accuracy. 



During the course of this work attention must also be 

 directed, as occasion arises, to such other bacteria, 

 pathogenic or saprophytic, as are allied to the particular 

 organisms under observation, or so resemble them as to 

 become possible sources of error, by working them 

 through on parallel lines in other words the various 

 bacteria should be studied in " groups." In the follow- 

 ing pages the grouping in use in the author's elemen- 

 tary classes for medical and dental students and for 

 candidates for the Public Health service is adopted, 

 since a fairly long experience has completely vindicated 

 the value and utility of this arrangement, and by its 

 means a fund of information is obtained with regard 

 to the resemblances and differences, morphological and 

 cultural, of a large number of bacteria. The fact that 

 some bacteria appear in more than one of these groups, 

 so far from being a disadvantage, is a positive gain to 

 the student, since with repetition alone will the neces- 



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