356 BAGTERIOLOOY. 



typhoid bacillus gains access to this viscus are likewise 

 open to other organisms present in the intestines, and 

 for this reason the bacterium coli commune, a normal 

 inhabitant of the colon, may also be found in this 

 locality. 



Note. — Obtain a pure culture of typhoid bacilli, and 

 from this make inoculations upon a series of potatoes 

 of different ages and from different sources. Do they 

 all grow alike ? 



Before sterilizing render another lot of potatoes 

 slightly acid with a few drops of very dilute acetic 

 acid; render others very slightly alkaline with dilute 

 caustic soda. Do any differences in the growth result ? 



Make a series of twelve tubes of peptone solution to 

 which rosolic acid has been added. Inoculate them all 

 with as near the same amount of material as possible 

 (one loopful from a bouillon culture into each tube); 

 place them all in the incubator. Is the color-change, 

 as compared with that of the control tube, the same in 

 all cases? 



Compare the morphology of cultures of the same age 

 on gelatin, agar-agar, and potato. 



Select a culture in which the vacuolations are quite 

 marked. Examine this culture unstained. Do the 

 organisms look as if they contained spores ? How 

 would you demonstrate that the vacuolations are not 

 spores ? 



Obtain from the normal feces a pure culture of the 

 commonest organism present. Write a full description 

 of it. Now make parallel cultures of this organism and 

 of the typhoid organism on all the different media. 

 How do they differ ? In what respects are they similar ? 



