320 



MANUAL OP BACTERIOLOGY. 



in animals when certain conditions are complied with. The 

 acid of the gastric juice destroys the organism, and this makes 

 it impossible to infect animals by way of the alimentary tract 

 unless this acidity is overcome with an alkaH before the intro- 

 duction of the culture. 



The following plan was adopted by Koch: 

 ^K 1^ The gastric juice was neutralized with a solu- 

 ^^^^^H tion of sodium carbonate; the movements of 

 ^^^^P^ the intestines were quieted by the injection of 

 TT I c.c. of tincture of opium for each 200 grams 



of the body-weight; and a portion of pure 

 culture of the cholera spirillum was intro- 

 duced into. the stomach. When guinea-pigs 

 are treated in this manner, in most cases a 

 condition closely simulating cholera is pro- 

 duced. The animal dies with symptoms of 

 collapse. The small intestine is more or less 

 filled with a watery, flocculent fluid containing 

 a large number of the spirilla of cholera. The 

 mucous membrane of the intestine is swollen 

 and reddened. 

 When mice or guinea-pigs receive an intra- 

 and Pjeip") " peritoneal injection from a pure culture, death 

 usually results, apparently from the toxic sub- 

 stances contained in the culture. Pfeiffer was the first to 

 show that an animal may be made immune from cholera by 

 repeated small doses of cultures which have been heated 

 in order to kill the organism. He also showed, in the same 

 connection, that when living comma bacilli are introduced 

 in the peritoneum of an immune animal they first clump 

 together and are then rapidly destroyed and disintegrated 

 (see page 192); furthermore, that a drop of the peritoneal 

 fluid added to a hanging-drop culture of the cholera spiriUum 

 produces the same effect. This is now called Pfciffer's ]ihc- 



FiG. 98. — Spiril- 

 lum or Chol- 

 era, Stae-cul- 

 TORE IN Gela- 

 tin, Two Days 



