36 CLINICAL BACTERIOLOGY AND 



Three films should then be made, dried, and stained : 



1. Carbol methylene blue. 



2. Carbol-fuchsin (Ziehl-Neelsen). 



3. Grain's method. 



Differential Diagnosis of the More Common Patho- 

 genic Cocci. 



A hanging-drop specimen should be made. 



A. Non-Motile. — 1. Staphylococci, single or in clumps. 

 2. Streptococci, single, pairs, or in chains. 3. Pneumo- 

 cocci, pairs or short chains. 4. Micrococcus tetragenus, 

 usually in fours. 5. Micrococcus catarrhalis, single or 

 pairs. 



(a) Gram-Positive. — (1) Staphylococci; (2) streptococci; 

 (3) pneumococci; (4) tetragenus. 



Staphylococci. 



Biological Characters. — 1. In broth the medium be- 

 comes turbid, with a white, yellow, or brown layer settling 

 at the bottom. 



2. On agar Staphylococcus albus forms a white, elevated 

 growth, moist and glistening. Staphylococcus aureus forms 

 a golden-yellow growth. Staphylococcus citreus forms a 

 lemon-coloured growth. 



3. In gelatin (stab culture) growth takes place along 

 the whole length of the puncture, followed by liquefaction 

 in two or three days, and ending in a deposit. 



Staining. — Methylene blue and Gram's. 



Microscopical Appearances. — Note characteristic bunches 

 of grape-like formation. 



Facultative Anaerobic. — Minimum temperature 6° C. ; 

 optimum, 35° C. ; maximum, 45° C. 



Streptococci. 



Biological Characters. — 1. In broth small granules de- 

 velop, growing sparingly. 



