6i 



EXERCISE XXX. 



BACILLUS COLI COMMUNIS (continued). 



§ 99. General Directions. Re-examine the cultures of 

 B. coli communis and note any changes which have occurred in 

 their appearance. Determine the gas formula in the fer- 

 mentation tubes of the different sugars. 



Place the milk and litmus milk cultures in the incubator 

 and keep them there for six weeks, noting the changes 

 which occur from week to week. 



Examine and describe fully the colonies on the gelatin 

 plates. Preserve the plates and examine them at the follow- 

 ing two exercises and note any changes which may have 

 occurred. 



Examine microscopically, in a stained preparation, the 

 bacteria from a colony on the gelatin plate. Preserve a prep- 

 aration to accompany the notes. 



Isolate B. coli communis from the intestine of an animal. 

 The intestine will be furnished. 



Inoculate, for Exercise XXXI a set of media with B. 

 cholerae suis and one with Bacillus typhosus from the cultures 

 furnished. 



§ 100. Isolating B. coli communis. Carefully open the 

 intestine by a longitudinal incision. Scrape away the con- 

 tents, if any, from a small area of the mucous membrane. 

 Take a loopful of the mucous from the surface of the 

 mucous membrane and inoculate a large tube of liquefied 

 gelatin with it. After shaking the tube carefully inoculate 

 a second tube with two loopfuls from the first, and a third 

 with three loopfuls from the second. Pour the gelatin into 

 Petri di.shes and label them. These plates should be exam- 

 ined daily. The colonies of B. coli communis can be distin- 

 guished from others which may appear by their thin spread- 



