INTRODUCTION 



Suggestions for the Use of the "Manual in Classifying 

 Unknown Organisms 



No organism can be classified before we have determined, through de- 

 tailed study, its morphological, cultural, physiological and pathogenic 

 characters. 



The characters used in the keys to orders, families and genera may ordi- 

 narily be determined by the use of a dozen or more of the procedures de- 

 scribed in the ^vlanual of Pure Culture Study issued by the Committee on 

 Bacteriological Technic (H. J. Conn, Chairman, Geneva, New York) of the 

 Society of American Bacteriologists. j\Iore complete examinations must 

 be made as indicated in the iNIanual of Pure Culture Study, and in the 

 Descriptive Charts which accompany this Manual where it is desired to 

 identify individual species. These tests must be made if bacteria are to be 

 accurately identified and described. 



It is urged that beginning students be taught the technics necessary for 

 the identification of species in the hope that the taxonomic work of the 

 future may be placed on a more satisfactory basis. 



After a complete study of the characters of the organism has been 

 made, turn to page 65 and ascertain first in which order the organism 

 belongs. When the order and suborder (if necessary) have been ascer- 

 tained, turn to the page of the IManual on which the key to that order or 

 suborder is given. In this key ascertain the family or subfamily to which 

 the organism belongs. 



When the family or subfamily has been decided on, again refer to the 

 page of the Manual on which the key to that familj^ or subfamily is given. 

 In this key ascertain the tribe to which the organism belongs. 



When the tribe has been decided on, again find the page of the Manual 

 on which the key to the tribe is given. In this key ascertain the genus 

 to which the organism belongs. 



When the genus has been decided on, again refer to the page of the 

 Manual on which the key to that genus is given. In this key, trace out 

 the species under investigation. 



For example, if one wishes to trace a short, peritrichous, Gram-negative, 

 non-spore-forming rod that grows well on ordinary culture media at 37°C, 

 fermenting glucose and lactose with production of acid and gas, not 

 liquefying gelatin, producing no pigment on any culture medium, with 

 negative reaction for acetylmethylcarbinol, producing indole and reducing 

 nitrates, consult the key to the orders on page 65. 



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