ROUTINE EXAMINATION OF MATERIAL 135 



case of the anthrax bacillus. The colonies on a plate having 

 been classified, a microscopic examination of each group may 

 be made by means of cover-glass preparations, and tubes of 

 suitable media are inoculated from each representative colony. 

 Each of the colonies used must be marked for future refer- 

 ence, preferably by drawing a circle round it on the under 

 surface of the plate or capsule with' a grease pencil, a number 

 or letter being added for easy reference. 



The general lines " along which observation is to be made 

 in the case of a particular bacterium may be indicated as 

 follows : — 



1. Microscopic Appearances. — For ordinary descriptive pur- 

 poses, young cultures, say of twenty-four hours' growth, on agar 

 should be used, though appearances in older cultures, such as 

 involution forms, etc., may also require attention. Note — (1) 

 the form ; (2) the size ; (3) the appearance of the protoplasmic 

 contents, especially as regards uniformity or irregularity of 

 staining ; (4) the method of grouping ; (5) the staining reactions. 

 Has it a capsule 1 Does the bacterium stain with simple watery 

 solutions 1 Does it require the use of stains containing 

 mordants t How does it behave towards Gram's method 1 It 

 is important to investigate the first four points, both when the 

 organism is in the fluids or tissues of the body and when growing 

 in artificial media, as slight variations occur. It must also be 

 borne in mind that slight variations are observed according to 

 the kind and consistence of the medium in which the organism 

 is growing. (6) Is it motile, and has it flagella 1 If so, how 

 •are they arranged^ (7) Does it form spores, and if so, under 

 what conditions as to temperature, etc. *? 



2. Growth Characteristics. — Here the most important points 

 on which information is to be asked are : What are the characters 

 of growth and what are the relations of growth (1) to tempera- 

 ture ; (2) to oxygen 1 These can be answered from some of the 

 following experiments : — 



A. Growth on gelatin. (1) Stab culture. Note — (a) rate of 

 growth ; (b) form of growth, (a) on surface, (/8) in substance ; (c) 

 presence or absence of liquefaction ; (d) colour ; (e) presence or 

 absence of gas formation and of characteristic smell ; (/) relation 

 to reaction of medium. (2) Streak culture. (3) Plate cultures. 

 Note appearances of colonies, (a) superficial; (b) deep. (4) Growth 

 in fluid gelatin at 37° C. 



B. Growth on agar at 37° C. (1) Stab. (2) Streak. Also 

 on glycerin-agar, blood-agar, etc. Appearances of colonies in 

 agar plates. 



