THE PNEUMOCOCCTJS, PNEUMONIA, ETC. 57 



is placed on a clean slide, another slide pressed upon it, and 

 the two are slid apart. The films thus obtained are allowed 

 to dry, and fixed by heat in the usual way. Another method, 

 a very good one, is to wash the mass of sputum under the tap 

 in a wire strainer, such as is used for tea. This can be steri- 

 lized in the flame before use, and the few organisms pre- 

 sent in good tap-water do not constitute serious contamina- 

 tions in cultures. (Parry Morgan.) 



One is then stained by Gram's method, and counterstained 

 by neutral red or dilute carbol fuchsin for about a quarter of 

 a minute, washed, dried, and mounted, and the other with 

 undiluted carbol fuchsin. 



The pneumococcus is a diplococcus i.e., the individual cocci 

 are arranged in pairs. Each coccus has usually an oval or 

 lancet shape, the sharp ends of the two germs pointing away 

 from one another (Plate I., Fig. 3, and Plate III., Fig. 4). 

 Abnormal forms (round cocci, short chains, short bacilli, etc.) 

 are frequent. The pneumococcus has a capsule when it occurs 

 in the living body or in pathological exudates, but not in most 

 cultures. This capsule does not stain readily, and appears in 

 a properly stained specimen as a clear halo round the two 

 cocci. 



Examine your Gram specimen first. The pneumococci 

 (which will be almost black) should be clearly seen, and you 

 should be able to make out their shape and characteristic 

 arrangement in pairs. 



The general surface of the film is stained pink, while there 

 is a clear and colourless zone round each pair of cocci. This 

 is the capsule, which is rendered distinct by "negative stain- 

 ing," and these appearances will be better seen in a somewhat 

 thick and deeply stained film, though if the carbol fuchsin has 

 been allowed to act too long the capsule may be stained a faint 

 pink. Occasionally the capsule has a great affinity for carbol 

 fuchsin, and stains more deeply than the surrounding film, 

 but this is unusual. There are special methods of staining 

 which may be used to render the capsule more distinct, but 

 these are usually unnecessary for the diagnosis. 



INTERPRETATION OF RESULTS. 



In cases of lobar pneumonia you will probably find pneu- 

 mococci in great quantity, and no other 1 bacteria in a specimen 



