118 CLINICAL BACTERIOLOGY. 



room-temperature, which, however, must not be too low. 

 Upon gelatin-plates the streptococcus grows in the form of 

 white, small, granular colonies that do not cause liquefac- 

 tion. With high powers of the microscope the chains can 

 distinctly be seen projecting beyond the margin of the 

 plate. In gelatin stab-culture there is no confluent growth ; 

 the line of inoculation can be seen distinctly to be made 

 up of individual colonies separated from one another. The 

 stab-culture on agar presents the same appearance. 

 Bouillon, which constitutes an admirable culture-medium 

 for streptococci, is usually not rendered turbid, but it 

 presents a flocculent crumbling sediment. Upon potatoes 

 only slight growth takes place. In milk the streptococcus 

 induces coagulation. It exhibits facultative anaerobiosis. 

 In' cultures the streptococcus dies much more quickly than 

 the staphylococcus within as short a time as four months. 

 Accordingly as the streptococci develop in bouillon into long 

 or short chains, a distinction has been made between strepto- 

 coccus longns and streptococcus brevis. Besides, a streptococcus 

 conglomerates has been distinguished that resembles super- 

 ficially the staphylococcus in the interlacing and adhesion 

 of the individual chains. This differentiation, however, 

 has had to be abandoned. In order to maintain the vir- 

 ulence of streptococci, Petruschky recommends their re- 

 newal in gelatin stab-cultures every five days, and their 

 preservation in the refrigerator. 



Diplococcus Pneumonias Frankel (Streptococcus Lanc- 

 eolatus Pasteur]. This organism is, as a rule, a nonmotile 

 coccus, arranged in pairs, with lancet-shaped extremities, and 

 frequently joined together in small chains. (Figs. 40, 41.) 

 They possess a capsule, which, however, is only clearly 

 visible in the products of disease, but which is usually ab- 

 sent in cultures. They stain readily, and also by Gram's 

 method. The capsule can be demonstrated by placing the 

 cover-glass preparation for a minute in I per cent, acetic 

 acid, drying, and then staining in aniline-water gentian- 

 violet. Johne's method of staining capsules may also be 

 employed (p. 108). The temperature-minimum is 22 C. 

 (71.6 F.) ; the temperature-maximum 39.5 C. (103.1 F.) 

 for cultures upon solid media, 42.5 C. (108.5 F.) for cul- 

 tures in fluid media ; the temperature-optimum from 3 5 C. 

 (95 F.) to 37 C. (98.6 F.). Upon gelatin the pneumo- 

 coccus appears at temperatures above 25 C. (77 F.) in 



