586 



PATHOGENIC MICROORGANISMS 



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

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

 distribution of about a hter 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. 127.: — Cholera SpiMLLtrM. 

 Fig. 128. — Cholera Spirillum. 

 Frankel and Pfeiffer.) 



Fig. 128. 



Stab Culture in Gelatin, three days old. 

 Stab Culture in Gelatin, six days old. (After 



60° C. kills them in an hour. In impure water, in moist hnen, 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).^ 



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 Fffrster, Hyg. Rundschau, 1893. 



