376 PATHOGENIC MICROORGANISMS 



more hardy and transplantation may safely be delayed for a week or 

 even longer. Albrecht and Ghon^ have kept a ciilture alive on agar 

 for one hundred and eighty-five days. It is a strange fact that after 

 prolonged artificial cultivation some strains of meningococcus may 

 gradually lose their growth energy and finally be lost because of their 

 refusal to develop in fresh transplants. Storage is best carried out at 

 incubator temperatures. At room temperatures or in the ice chest, 

 the diplococcus dies rapidly.^ 



Resistance- — ^The meningococcus is killed by exposure to sunlight or 

 to drying within twenty-four hours.' It is extremely sensitive to heat 

 and cold and by the common disinfectants is killed in high dilutions 

 and by short exposures. At 0° C. it usually dies within two or three 

 days. 



Pathogenicity. — As stated above, the form of meningitis caused by 

 the diplococcus of Weichselbaum occurs usually in epidemics, though 

 isolated sporadic cases are seen from time to time in aU crowded com- 

 munities. Epidemics have been numerous and widespread, and their 

 records far antedate the discovery of their causative agent. As a rule, 

 these epidemics have occurred during the winter and spring months, 

 and have attacked chiefly that part of the population which is forced by 

 poverty to live in crowded unhygienic surroundings. The manner in 

 which the microorganism enters the human body is still a subject for 

 investigation. Weichselbaum,^ Ghon and Pfeiffer,' and, more recently, 

 Goodwin and v. ShoUy ° of the New York Department of Health, have 

 succeeded in demonstrating culturally the presence of the meningococ- 

 cus in the nasal cavities, not only of patients suffering from the disease, 

 but occasionally in those of healthy subjects as well. Similar findings 

 have been reported by many others; but in many cases morphological 

 examination only was made, which, owing to the danger of confusion 

 with Micrococcus catarrhalis, a frequent inhabitant of the nose, renders 

 such reports valueless. The careful work of the writers mentioned, how- 

 ever, has given ground for the theory that meningeal infection, which is 



^Albrecht und Ghon, Wien. klin. Woch., 1901. 



2 A very thorough biological study of meningococcus and related organisms has 

 recently been made by Elser and Huntoon (Jour. Med. Res., N. S. vol. xv, 1999), 

 which may be consulted for a more detailed description of cxiltiu-al characteristics. 



' Councilman, Mallory, and Wright, Boston, 1898; Albrecht and Ghon, loc. cit. 



< Weichselhaum, Fort. d. Med., 1887. 



^Ghon und Pfdffer, Zeit. f. klin. Med., xUv, 1901. 



« Goodwin und v. Sholly, Jour. Inf. Dis., Suppl. 2, Feb., 1906. 



