APPLICATION OF THE METHODS OF 

 BACTERIOLOGY. 



CHAPTER XIY. 



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 de- 

 posit. 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 

 oi^nisms composing each of them will always produce 



