APPLICATION OF THE METHODS OF 

 BACTERIOLOGY. 



CHAPTER XIV. 



To obtain material with which to begin work. 



EXPOSE to the air of an inhabited room a slice of 

 freshly steamed potato or a bit of slightly moistened 

 bread upon a plate for about one hour. Then cover it 

 with an ordinary water-glass and place it in a warm spot 

 (temperature not to exceed that of the human body 

 37.5 C.), and allow it to remain unmolested. At the 

 end of twenty-four to thirty-six hours there will be 

 seen upon the cut surface of the bread or potato small, 

 round, oval, or irregularly round patches which present 

 various appearances. 



These differences in macroscopic appearance are due, 

 in some cases, to the presence or absence of color ; in 

 others to a higher or lower degree of moisture ; in some 

 instances a patch will be glistening and smooth, while its 

 neighbor may be dull and rough or wrinkled ; here will 

 appear an island regularly round in outline, and there 

 an area covered by an irregular ragged deposit. All 

 of these gross appearances are of value in aiding us to 

 distinguish between these colonies for colonies they 

 are and under the same conditions the organisms com- 



