ROUTINE TESTS FOR THE DESCRIPTIVE CHART v«-5 



first appears the proper descriptive terms on tlie Chart shouhl be 

 underhiied. Any changes occurring and noted in subsequent study 

 should also be recorded on the Chart. The meaning of the terms 

 given in this section of the Chart will in general be made clear by 

 consulting the glossary included in Leaflet I. 



Variation 

 In using these methods it must be remembered that among bac- 

 teria, the individual members of any species may differ from each 

 other in respect to both physiology and morphology, thus making it 

 difficult to define the limits of the species; also that any individual 

 culture in repeated examinations may produce variable results in 

 connection with some test even when studied under apparently con- 

 stant conditions. For these reasons it is important that single deter- 

 minations shall never be used for characterizing any culture that has 

 been studied, or much less for characterizing any species or type 

 that is being described. Determinations must be repeated at differ- 

 ent times and under different conditions in order to learn definitely 

 the physiological characteristics of a culture. Whenever possible, an 

 effort should be made to correlate the variations in physiology and 

 serology with colony typo and to list sej)arately the ])hysiological 

 characteristics of the "smooth", "rough", "mucoid", "opaque", 

 "translucent" strains, etc. When an organism shows any tendency 

 to "dissociate" into "phase variants", its description is incomplete if 

 it applies to only one phase or to a culture containing a mixture of 

 two phases or more. In such case the phase variants should be 

 separated by plating methods, or otherwise, and a separate chart 

 should be used for each individual strain studied. The individual 

 charts may be filed for the investigator's information; but it must be 

 insisted that results of such work should not be published for the use 

 of other bacteriologists until repeated determinations have l)een made 

 and, if possible, have been shown to bear some relation to the j)hase 

 indicated by colony type. 



Cultural Characteristics 



Space is provided on both Charts for recording appearance of 

 colonies, growth on agar stroke, in broth and gelatin stab. In ad- 

 dition to the space i)rovided for sketches, various terms are listed in 

 order that those which apply may be underlined. The meaning of 

 all the terms is given in the Glossary in Leaflet I. 



As some of the terms, especially in regard to shape and struct ur(> of 

 colonies, are more easily described graphically than verbally the 

 diagram on page 7 (also published separately) is included here to 

 assist the student in understanding the appropriate terms. 



