264 CLINICAL BACTERIOLOGY. 



usual way for examination. The microscopic examination is 

 best made by means of an oil-immersion lens ; slightly curved 

 bacilli stained red are looked for, and if these are found, they 

 can be tubercle-bacilli only. At times the spores of mold-fungi 

 and of bacilli, portions of hair, fragments of horny epithelial 

 cells, cholesterin-plates, crystals of fatty acids, and similar ele- 

 ments, stained red, are observed, which have resisted decolor- 

 ization ; but a little experience will prevent confusion of these 

 with tubercle-bacilli. 



Decolorization and counterstaining may be practised together 

 (B. Frankel-Gabbet) by adding the decolorizing acid to the 

 solution employed in counterstaining. After staining with 

 hot carbol-fuchsin solution the cover-slip preparation, rinsed in 

 water, is placed in the following solution : Nitric acid 20, 

 alcohol 30, water 50, methylene-blue to saturation. After 

 washing with water the preparation is dried and mounted in 

 the usual manner. 



In order to find the tubercle-bacilli when these are present in 

 small number, it is advisable, according to the suggestion of 

 Biedert, to dilute the sputum in a test-tube with water, to add 

 potassium or sodium hydroxid, and to continue the application 

 of heat until the fluid assumes a homogeneous appearance. Sed- 

 imentation is then permitted to take place, and the bacilli, by 

 reason of their weight, sink to the bottom of the tube. The 

 sediment is then examined by one of the methods just de- 

 scribed. 



(^) Examination of Feces. A flake of mucus or of pus is 

 selected from the feces, and treated precisely in the manner de- 

 scribed for sputum. 



(c} Demonstration of Tubercle-bacilli in Urine. The urine, 

 which is usually turbid from the presence of pus, is permitted 

 to settle in a conical glass, or it is centrifugated. The sediment 

 is placed upon a cover-slip in a somewhat thicker layer than the 

 sputum, but in other respects it is treated in exactly the same 

 manner. In urine the tubercle-bacilli are prone to lie together 

 in small masses (nests). 



(d ) Pus from cold abscesses and fluid from pleural effusions 

 suspected to be tuberculous are often examined in vain for tuber- 

 cle-bacilli. After intraperitoneal injection of such material 

 (possibly after centrifugation) guinea-pigs not rarely die of 

 experimental tuberculosis. In this way it is possible, although 

 after the lapse of weeks, to make a diagnosis of the presence of 

 tubercle-bacilli. 



(e) Staining of Tubercle-bacilli in Sections. The staining of 

 sections in hot solutions is not practicable. The preparations 

 are, therefore, kept in the aniline-water staining solution or the 

 carbolfuchsin for from twelve to twenty-five hours at room-tern- 



