288 WATER HYGIENE 
III. Biological characters. 
A. Cultural growth in or on nutrient broth, gelatin plates, 
gelatin tubes, agar plates, agar tubes, potato, milk and 
blood serum. 
B. Biochemical. 
Temperature relations, relation to oxygen, acidity of 
medium action on gelatin, protein, carbohydrates, 
nitrates, indol, pigments and odor. 
C. Pathogenesis. 
Optional Tests: 
I. Morphological. 
Staining reactions, study of flagella by special stains, perma- 
nency of characters. 
II. Physiological. 
A. Cultural. 
Growth—litmus gelatin, blood serum, synthetic media, 
photograph. 
B. Biochemical. 
Maximum, minimum and optimum temperature of 
growth, growth in special gases, limit of acid and 
alkali, chemical properties of pigments. 
C. Pathogenesis. 
Inoculation, toxins, ete. 
At the end of the report are given charts for recording the characters of 
bacteria. This is one of the first attempts in which the organized efforts 
of a society were brought to bear in systematizing methods for the study 
of the bacterial cell. 
Marshall Ward (1897) in studying the bacterial flora of the Thames 
river arranged his strains into the following groups: 
I. Forms identical with Bacterium uree. 
IT. Violet bacteria. 
III. B. fluorescens liquefaciens group. 
IV. B. fluorescens non-liquefaciens group. 
V. Typical B. cola communis. 
VI. Series of forms centering around B. proteus. 
VII. Like VI except that a yellow pigment is formed. 
VIII. Bacteria between VII and IX. Characters changed. 
IX. Golden yellow liquefying forms. 
