HOW BACTERIA ARE NAMED AND IDENTIFIED 47 



(4) Order. An order is a group of related families. It is named usually 

 (not always) by substituting the suffix -ales for -aceae in the name of the 

 type family. Among ordinal names that have been used in bacteriology 

 are Actinomycetalcs, Spirochaetales, Euhaderiales. 



(5) Class. A class is a group of related orders. In this treatise it is 

 considered that the bacteria constitute a class of the plant kingdom, and 

 this is named ScMzoniycetes. 



(6) Other categories. Other categories or ra7iks of names are used for 

 higher groups. Sometimes families are divided into sub-families, these 

 into tribes, these into sulitribes, and these finalh^ into genera. 



How to identify an organism by name. One of the main purposes of a 

 manual of determinative bacteriology is to facilitate the finding of the 

 correct scientific name of a bacterium. Such is the purpose of this volume. 

 It is well, however, to note some of the reasons why this result, the identifi- 

 cation of an unknown culture, may not eventuate. Among these reasons 

 the following may be listed : 



(1) The unknown organism awaiting identification bj' the investigator 

 may easily be one which has never been named, or perhaps adequately 

 described. For the most part there has been little effort on the part of 

 bacteriologists to describe or name bacteria except as they have been found 

 to have some economic significance or possess some striking or unusual 

 characteristics. It is quite probable that there are manj^ times as many 

 species of bacteria undescribed and named as have been described. Such 

 undescribed species are all about us. It is not surprising, therefore, if one 

 frequently encounters undescribed species. When such unnamed species 

 are encountered, particularly if they are of economic importance or are 

 related to such forms, it is highly desirable that they should be described, 

 named and the results published and made accessible. 



(2) The unknown organism may have been described and named in 

 some publication, but the description and name have been over-looked in 

 the preparation of the AIaxual. Perhaps the description has been so 

 inadequate or incomplete that it has not been possible to place it in the 

 classification. It should be noted that the number of species that have 

 been described is so great that no one individual can know them all. 

 Progress in classification comes about largely as the result of the work of 

 specialists in particular groups. For example. Ford made a studj- of all 

 of the aerobic spore-bearing bacteria which he had secured from various 

 sources. He studied also the descriptions of such bacteria in the literature, 

 and then monographed the group. Similar studies on other groups have 

 resulted in more or less complete monographs. Such, for example, are the 

 monographs on the intestinal group by Welden and Levine, of the acetic 

 bacteria by Hoyer, and Visser 't Hooft, of the cocci b}^ Hucker, of the 



