338 Pneumonia 



Virulence. Pneumococci vary greatly in virulence, and 

 rapidly lose this quality in artificial culture. When it is 

 desired to maintain or increase the virulence, a culture must 

 be frequently passed through animals. Washbourn found, 

 however, that a pneumococcus isolated from pneumonic 

 sputum and passed through one mouse and nine rabbits 

 developed a permanent virulence when kept on agar-agar 

 so made that it was not heated beyond 100 C., and alka- 

 linized 4 c.c. of normal caustic soda solution to each liter 

 beyond the neutral point determined with rosolic acid. 

 The agar-agar is first streaked with sterile rabbit's blood, 

 then inoculated. The cultures are kept at 37.5 C. Ordi- 

 narily pneumococci seem unable to accommodate them- 

 selves to a purely saprophytic life, and unless continually 

 transplanted to new media die in a week or two, some- 

 times sooner. Lambert found, however, that in Marmorek's 

 mixture of bouillon 2 parts and ascitic or pleuritic fluid 

 i part, the organisms would sometimes remain alive as long 

 as eight months, preserving their virulence during the entire 

 time. 



Virulence can also be retained for a considerable time by- 

 keeping the organisms in the blood from an infected rabbit, 

 hermetically sealed in a glass tube, on ice. 



Bacteriologic Determination. It is usually unnecessary 

 to call upon the bacteriologist to assist in making the diagno- 

 sis of pneumonia. If necessary, the expectoration can be 

 examined by the methods already given for staining the 

 pneumococcus, or rabbits may be inoculated and the organ- 

 ism recovered from the blood. Caution must be exercised 

 in using this means of diagnosis, however, as the organ- 

 ism sometimes occurs in normal saliva, and is a common 

 associated organism in tuberculosis and other respiratory 

 diseases. Wadsworth* has been able to show that agglu- 

 tination reactions can be obtained by concentrating the 

 pneumococci in isotonic solution and adding the serum. 

 The method does not seem easily applicable for diagnosis. 



Buergert found that all pneumococci irrespective of 

 source were agglutinated by pneumococcus immune serum, 

 that such serum was capable of agglutinating various pyo- 

 genic streptococci, certain atypical organisms and certain 

 strains of Streptococcus mucosus capsulatus. The sera of 



* "Jour. Med. Research," vol. x, p. 228, 1904. 

 f "Jour. Exp. Med.," Aug. 25, 1905, vn, No. 5. 



