586 



PATHOGENIC MICROORGANISMS 



For isolation of the bacteria from water, it is, of course, necessary 

 to use comparatively large quantities. Fliigge l and Bitter advise the 

 distribution of about a liter of water in ten or twelve Erlenmeyer flasks. 

 To each of these they add 10 c.c. of sterile pepton-salt solution (pepton 

 ten per cent, NaCl five per cent). After eighteen hours at 37.5 C. the 

 surface growths in these flasks are examined both microscopically and 

 culturally as before. 



Biological Considerations. The cholera spirillum is aerobic and 

 facultatively anaerobic. It does not form spores. The optimum tem- 

 perature for its growth is about 37.5 C. It grows easily, however, at a 

 temperature of 22 C. and does not cease to grow at temperatures as 

 high as 40. Frozen in ice, these bacteria may live for about three 

 or four days. Boiling destroys them immediately. A temperature of 



FIG. 127. 



FIG. 128. 



FIG. 127. CHOLERA SPIRILLUM. Stab Culture in Gelatin, three days old. 

 FIG. 128. CHOLERA SPIRILLUM. Stab Culture in Gelatin, six days old. (After 

 Frankel and Pfeiffer.) 



60 C. kills them in an hour. In impure water, in moist linen, and in 

 food stuffs, they may live for many days. Associated with sapro- 

 phytes in feces and other putrefying material, and wherever active 

 acid formation is taking place, they are destroyed within several days. 

 Complete drying kills them in a short time. The common disin- 

 fectants destroy them in weak solutions and after short exposures 

 (carbolic acid, five-tenths per cent in one-half hour; bichlorid of 

 mercury, 1 : 100,000 in ten minutes; mineral acids, 1 : 5,000 or 10,000 

 in a few minutes) . 2 



Pathogenicity. Cholera is essentially a disease of man. Endemic in 

 India and other Eastern countries, it has from time to time epidemically 

 invaded large territories of Europe and Asia, not infrequently assuming 



1 Fliigge, Zeit. f. Hyg., xiv, 1893. 



2 Forster, Hyg. Rundschau, 1893. 



