92 SPECIAL BACTERIOLOGY 



Biological Characters. Grows in the presence of oxygen, aerobic, 

 but is also a facultative anaerobe. Under the latter conditions it retains 

 its vitality and virulence much longer. The minimum temperature for 

 its growth is 22 C., maximum 39 '5 C. for cultures on solid media, and 

 42-5 C. for those on liquid media, while the optimum temperature is 35 

 to 37 C. 



On Gelatine at 25 it develops fine delicate colonies. The gelatine 

 is not liquefied. 



On Oblique surface agar (which must be only slightly alkaline). On 

 Agar Plates and blood serum the diplococci grow in small, fairly 

 granular dewdrop-like colonies. 



In Bouillon the growth exhibits nothing characteristic. 



Milk is a favourable medium, and in some cultures coagulation 

 results. 



The diplococci grow best on media containing blood. 



Vitality. Pneumonic sputum attached to cloths, air-dried, and 

 exposed to diffuse daylight, retained its virulence for rabbits in one 

 series of experiments for a period of 19 days, and in another series for 

 55 days. Exposed to direct sunlight, the same material retained its 

 virulence after twelve hours' exposure. In agar cultures the diplococci do 

 not live long (four or five days), but in bouillon their vitality is more 

 prolonged. The cause of the cultures dying is the formation of lactic 

 and formic acids. Neutralizing the cultures with calcium carbonate 

 causes them to retain their vitality for months. Exposure for ten 

 minutes at 52 C. is sufficient for their destruction, and they exhibit very 

 slight resistance to the ordinary germicides. 



Pathogenesis. The diplococci of pneumonia are pathogenic for 

 rabbits, guinea-pigs, and mice. Rabbits infected subcutaneously with 

 a fresh virulent bouillon culture die in one to two days of a typical 

 septicaemia; rats are less susceptible to infection, and chickens and 

 pigeons are immune. Kruse and Pansini also found a sheep and a 

 horse immune. 



BACILLUS OF PNEUMONIA (FRIEDLANDER). 



This organism is seldom found in pneumonic patients. It occurs 

 either alone or associated with other organisms, and is frequently 

 found in the nasal discharge in catarrh, and in otitis media acuta. 



Microscopical Appearances. The bacilli are much larger than 

 the diplococcus of pneumonia, the minimum size being 1 p. They are 

 arranged in diplo-formation or in chains. A capsule is present in 

 specimens from sputum and inoculated animals, and it can also some- 

 times be observed in specimens prepared from cultures. (See Photo- 

 micrograph, Fig. 29.) 



