TUBERCLE 6l 



the stain from being removed by such substances as acids and 

 alcohol. In stage 3 of the above process we aim at allowing the 

 acid to act until it has removed the fuchsin from everything 

 except the tubercle bacilli. The methylene blue is a counter- 

 stain, and colours all organisms, pus cells (especially their nuclei), 

 epithelial cells, and shreds of lung-tissue — in fact, everything 

 except the tubercle bacilli. The latter appear as slender red rods, 

 which often show the irregular staining which has been described 

 as occurring in the diphtheria bacillus. 



Now, " acid-fast " bacilli are very rare, though they have been 

 found in unexpected situations of late years. Only three such 

 bacilli need be taken into consideration in dealing with human 

 pathology. These are the tubercle bacillus, the leprosy bacillus, 

 and the smegma bacillus. The bacillus of leprosy would rarely 

 lead to mistakes in this country ; it is recognized by the fact that 

 it is straighter and more uniform than the tubercle bacillus, and 

 by the fact that it resists decolorization more powerfully than the 

 tubercle bacillus. The smegma bacillus may occur in the urine, 

 and lead to mistakes unless the sample examined was drawn off 

 pev catheter. It is distinguished by the fact that it is readily 

 decolorized by alcohol (absolute alcohol or methylated spirit), 

 while the tubercle bacillus is not. In staining a film from the 

 urine, we decolorize in spirit for a quarter of an hour after the 

 acid and before the methylene blue — i.e., between stages 3 and 4 

 in the above description. 



In searching for the tubercle bacillus, the |-inch lens will serve, 

 though an oil-immersion lens is an advantage. 



Method of Collecting the Sputum. 



This is of some importance, and the method recommended 

 should be carried out in all cases. 



Get the patient to wash out his mouth thoroughly with warm 

 water before going to bed. Let him spit into a clean bottle, jar 

 or tin, and employ only the sputum coughed up before food is 

 taken in the morning. 



It is often impossible to get sputum from children, but in them 

 it is often possible to pick masses of sputum out of the vomit and 

 to demonstrate tubercle bacilli therein ; and when no such masses 

 are seen, bacilli may occasionally be found if the whole vomit be 

 carbolized in the manner described subsequently and the sedi- 



