212 PA THOGENIC BA CTERIA . 



The physician will secure a better result if the exam- 

 ination be made on the same day than if he wait a num- 

 ber of days, because if the bacilli are few they occur 

 most plentifully in the small caseous flakes to be de- 

 scribed farther on, which are easily found at first, but 

 which break up and become part of a granular sediment 

 that always forms in decomposed sputum. 



The fresh sputum when held over a black surface 

 generally shows a number of grayish-yellow, irregular, 

 translucent granules somewhat smaller than the head of 

 a pin. These consist principally of the caseous material 

 from tuberculous tissue, and are the most valuable part 

 of the sputum for examination. One of the granules is 

 picked up with a pointed match-stick and spread over 

 the surface of a perfectly clean cover-glass. If no such 

 fragment can be found, the purulent part is next best for 

 examination. The mucus itself rarely contains bacilli 

 when free from scraps of tissue and pus. 



In cases in which this ordinary procedure fails to reveal 

 bacilli whose presence is strongly indicated by the clin- 

 ical signs, the exact method of searching for them is to 

 partially digest the sputum with caustic potash, and then 

 collect the solid matter with a centrifugal apparatus. If 

 a very few bacilli are present in the sputum, this method 

 will often secure them. 



The material spread upon the cover-glasses should not 

 be too small in amount. Of course a massive, thick 

 layer will become opaque in staining, but should the 

 layer spread be, as is often advised, " as thin as possible," 

 there may be too few bacilli upon the glass to enable one 

 to make a satisfactory diagnosis. 



As usual, the material is allowed to dry thoroughly, 

 and is then passed three times through the flame for 

 purposes of fixation. 



Ehrlictfs Method, or the Koch-Ehrlich Method. The 

 cover-glasses thus prepared are floated, smeared side 

 down, upon, or immersed, smeared side up, in, a small 

 dish of Ehrlich's anilin-water gentian-violet solution : 



