530 APPLICATION OF METHODS OF BACTERIOLOGY 



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. Are 

 any differences in the growths noticeable ? 



Make a series of twelve tubes of peptone solution to which 

 rosolic acid has been added. Inoculate them all with as 

 nearly 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? What is the crucial 

 test for spores? 



Obtain from normal feces a pure culture of the com- 

 monest organism present. Write a full description of it. 

 Now make parallel cultures of this organism and of the 

 typhoid bacillus on all the different media? How do they 

 differ? In what respects are they similar? 



BACILLUS COLI (ESCHERICH), MIGULA, 1900. 



SYNONYMS: Bacillus neapolitanus, Emmerich, 1884; Bacillus pyogenes 

 fcetidus, Passet, 1885; Emmerich's bacillus, Eisenberg, 1886; Bacterium 

 coli commune, Escherich, 1886. 



This organism was discovered by Escherich, in 1886, in 

 the intestinal discharges of milk-fed infants. It has since 

 been demonstrated to be a constant inhabitant of the intes- 

 tines of man and domestic animals, and is, therefore, con- 

 sidered a commensal species. 



