142 AIDS TO BACTERIOLOGY 



Flexner's curative serum has been used with success 

 (Lancet, October 30, 1909), and has considerably dimin- 

 ished the mortality, but it is important to obtain a serum 

 which is polyvalent to as many strains as possible. A 

 serum prepared from one strain may be entirely ineffective 

 when used to combat infection with a meningococcus 

 morphologically and culturally identical. 



The judicious use of polyvalent vaccines is said to have 

 met with frequent success. Colebrook (Medical Press, 

 May 12, 1915) states that the vaccine did not help to 

 eradicate the meningococcus from the naso-pharynx 

 of carriers with any regularity. 



CHAPTER XI 



The Diplococcus (Streptococcus) Pneumonise. 



Morphology. D. pneumonice is found in large numbers 

 in the affected lung and in the rusty expectoration of 

 acute croupous or lobar pneumonia, and occasionally in 

 the blood. It is seen usually as a diplococcus, sometimes 

 in chains of four elements. The cocci are oval or lance- 

 head shaped, measure 0'5 JLL by TO [JL, and are surrounded 

 with marked gelatinous capsules. The organism is 

 Gram-positive. Maynard (Med. Press, November 4, 

 1914) thinks it probable that the pneumococcus can 

 assume the form of a bacillus of diphtheroid type. 



Cultural Characters (see also Streptococci, pp. 134, 

 15). The pneumococcus is an aerobe and facultative 

 anaerobe. It grows well on blood-serum and glycerin 

 agar at 37 C., but the dewdrop growth is only visible on 

 close examination. On gelatin at room-temperature it 

 does not develop. Under cultivation the capsule is lost, 

 except in media containing blood-serum, and it forms 

 short chains of a few cocci; hence it is probably a strepto- 

 coccus. It rapidly (five to six days) loses its vitality on 

 agar, but can be preserved alive for a considerable time 

 on agar smeared with blood or in gelatin kept in the 

 blood-heat incubator. It does not- develop on potato. 

 It grows in milk, with the production of acid, and usually 

 with curdling. 



