ROUTINE TESTS FOR THE IDENTIFICATION OF BACTERIA 143 



gin for recording the most important characteristics by a system of 

 numerical notation. 



The special feature of the Standard Descriptive Chart is that all the 

 most important characteristics of an organism may be recorded on the 

 front of the sheet, partly in the margin, partly in the larger section at the 

 right, while the fermentative reactions are to be entered at the bottom. 

 By the use of right-hand margin and bottom edge, a long series of charts 

 may be compared, one on top of the other, by glancing only at these two 

 edges. The back of the Standard Chart is now reserved largely for sup- 

 plementary data, nearly all of which is summarized on the front. (See 

 Fig. 2.)^ 



The increasingly large number of tests called for in the study of bac- 

 teria has resulted in making a somewhat complicated chart. Although 

 all these tests may be needed in some research work, they plainly are not 

 needed in the use of the chart for instruction purposes. To meet the 

 demand for a simpler chart for use in teaching, a new form known as the 

 Descriptive Chart for Instruction was published in 1939. This chart is 

 designed to fit a standard notebook for 11- by 83^-in. sheets. (See 

 Fig. 3.) In numerous research laboratories, also, this chart is proving 

 more useful than the Standard Chart because of its flexibility and the 

 amount of space available for special tests. 



DETERMINING OPTIMUM CONDITIONS FOR GROWTH 



Before beginning the study of any pure culture, it is important to know 

 something about the growth requirements of the organism. If the 

 organism in question does not grow in ordinary media, because it requires 

 the complete absence either of oxygen or of organic matter (or has other 

 ''special" requirements), it obviously cannot be studied by the methods 

 called for on the Descriptive Chart. For such organisms the investigator 

 must use his own methods of study and may record the results in the 

 blank space at the bottom of the back of the chart. For those organisms 

 that grow on ordinary media, methods must be varied according to 

 whether the organisms grow better in liquid or in solid media and at high 

 temperature or low temperature. It is important, therefore, that before 

 an unknown culture which is able to grow in laboratory media is studied, 

 these two points in regard to growth requirements be determined. (As 

 pointed out in Chap. Ill, many such media are now available in dehy- 

 drated form.) 



Bacteria may not grow well upon ordinary laboratory media when they 

 are first isolated. In some instances cultures may be adapted to the 

 media used for routine testing of cultural properties through a series of 



