PNEUMONIA. 119 



Morphology. Jttcrocoecus pneumonia? is a small oval coccus 

 appearing alone or united in pairs, occasionally forming chains 

 with four or five elements resembling streptococci. In the 

 animal body it is generally oval and double, as a diplococcus, 

 surrounded by a capsule (Fig. 50). 



In solid media it grows as a micrococcus, a diplococcus, or 

 as a chain like the streptococcus with scarcely more than four 

 or five elements. In liquid media the cells are more nearly 

 round, and the chains contain sometimes as many as eight or 

 ten elements (Fig. 51). 



It stains by the anilin dyes, and also by Gram's method. 



Biologic Characters. The Hficrococeus pneumonice is aerobic 

 and facultative anaerobic. Like most cocci it is non-motile, 

 and therefore has no flagella. It grows on all culture-media, 

 very little at a temperature below 24 C., best at a tempera- 

 ture of 37 C. At a temperature above 42 C. all growth 

 ceases. It is killed in a few minutes by exposure to a tem- 

 perature of 52 C. If grown at 42 C. for twenty-four hours, 

 its culture becomes very much attenuated, practically losing 

 its virulence. In sputum it lives a long time. Twenty per 

 cent, alcohol is the best disinfectant (Wadsworth). 



In bouillon it grows rapidly, and in twenty-four hours 

 causes a distinct cloudiness of the medium. At the end of 

 forty-eight hours its growth ceases, and in four or five days 

 the bouillon becomes clear again, the bacillary growth being 

 deposited at the bottom of the tube. In 15 per cent, gelatin 

 at 24 C. its growth is slow. The gelatin is not liquefied. 

 On blood-serum at the temperature of 37 C. it grows as clear, 

 almost transparent spots. Its growth on agar is very much 

 like that on blood-serum. It does not grow on potato. It 

 causes coagulation of milk. Hiss has devised a medium for 

 the differentiation of streptococci and pneumococci. It con- 

 sists of beef serum, 1 part, distilled water, 2 parts, to which 

 is added 1 per cent, inulin (Inulin C. P.) and enough litmus 

 to render the medium a clear transparent blue. Pneumococci 

 ferment the inulin with acid production, rendering the litmus 

 red, ; ;in<l the medium is coagi dated. Streptococci do not have 

 tli is effect 



