PATHOGENIC BACTERIA. 103 



dish or beaker full of carbol-fuchsin for eight to ten hours, and 

 then decolorized and counterstained in the usual way. The 

 method is less liable to produce artefacts than the quick 

 method, but is not much used on account of the time it takes. 



BiederVs Method of Collecting Bacilli, when the bacilli are 

 very few in a great quantity of fluid, as urine, pus, abundant 

 mucus, etc., Biedert advises to mix 15 c.cm. of the fluid 

 with 75 to 100 c.cm. water and a few drops of potassium or 

 sodium hydrate, then boiling until the solution is quite thin. It 

 is placed in a conical glass for two days, and bacilli with other 

 morphological elements sink to the bottom of the glass ; when 

 the supernatant liquid is decanted, the residue can be easily 

 examined. In this way bacilli were found that had eluded 

 detection examined in the ordinary manner. 



The centrifugal machine is used either in connection with 

 Biedert's sediment method or without, to obtain the solids sus- 

 pended in urine or serum. 



When the bacilli are so few in number in sputum or urine as 

 to make their detection difficult, and also when doubt exists as 

 to the identity of acid-fast bacilli found, several guinea-pigs 

 should be injected in the groin and smears and sections made 

 from the enlarged glands resulting. 



Carbolic Acid to Sediment Sputum. Pure carbolic acid added 

 to sputum (about 1 part of the acid to 6 parts of sputum) will 

 in a few hours produce a coagulation and allow the sputum to 

 be spread evenly on the cover-glass, showing greater collections 

 of bacilli. 



Without cover-glass. Sputum can be spread and stained on 

 the glass slide without the use of a cover-glass, the oil of cedar 

 being placed directly on the stained sputum, and the oil immer- 

 sion lens dipping into it. It is a rapid and cheap way ; and 

 when a given case is to be studied daily the method is useful. 



Pure Cultures from Sputum. Kitasato recommends the tho- 

 rough washing, changing the water ten times, of the small masses 

 found in the sputum of tubercular persons. When such speci- 

 mens are examined they show tubercle bacilli alone, and when 

 inoculated in agar give rise to pure cultures. 



Staining Bacillus Tuberculosis in Tissue (sections}. The general 



