METHODS OF EXAMINATION 297 



for immunising animals whose serum he states is suitable for the treat- 

 ment of human cases. 



Methods of Examination.— (l) Microscopic Examination.— Tuberculosis 

 is one of the comparatively few diseases in which a diagnosis can usually 

 be definitely made by microscopic examination alone. In the case of 

 sputum, one of the yellowish fragments which are often present ought to 

 be selected ; dried films are then prepared in the usual way, and stained 

 by the Ziehl-Neelsen stain (p. 105). In the case of urine or other fluids, 

 a deposit should first be obtained by centrifuging a quantity in a test- 

 tube, or by allowing the fluids to stand in a tall glass vessel (an ordinary 

 burette is very convenient). Film preparations are then made with the 

 deposit and treated as before. If a negative result is obtained in a 

 suspected case, repeated examination should be undertaken. To avoid 

 risk of contamination with the smegma bacillus, the meatus of the urethra 

 should be cleansed and the urine first passed should be rejected, or the 

 urine may be drawn off with a sterile catheter. As stated above, it is 

 only exceptionally that difficulty will arise to the experienced observer 

 from this cause. (For points to be attended to, vide p. 286.) The detec- 

 tion of tubercle bacilli by microscopical methods in sputum, pus, feces, 

 and even tissues, has been greatly facilitated by the introduction of a 

 preparation called " antiformin." This is a mixture of equal parts of 

 liquor sodie chlorinatse (B. P. ) and of a 15 per cent, solution of caustic 

 soda. It has a remarkable disintegrative and dissolving action on the 

 tissues, etc., so that after it has been allowed to act on sputum, for ex- 

 ample, and the mixture is eentrifuged, the resulting deposit is scanty and 

 the tubercle bacilli, if present, are accordingly greatly concentrated. The 

 time necessary may be judged of by the appearance of the mixture, but it 

 will generally be found that the desired result will be obtained after about 

 an hour if one part of sputum be added to two or three parts of 20 per 

 cent, antiformin; the mixture should be shaken from time to time, 

 especially when the sputum is tenacious. 



(2; Inoculation. — The guinea-pig is the most suitable animal. If the 

 material to be tested is a fluid, it is injected subcutaneously or into the 

 peritoneum ; if solid or semi-solid, it is placed in a small pocket in the 

 skiu, or it may be thoroughly broken up in sterile water or other fluid and 

 the emulsion injected. By this method, material in which no tubercle bacilli 

 can be found microscopically may sometimes be shown to be tubercular. 



(3) Cultivation. — The best method to obtain pure cultures is to produce 

 tuberculosis in a guinea-pig by inoculation with tubercular material, and 

 then, killing the animal after four or five weeks, to inoculate tubes of 

 solidified blood serum or egg medium, under strict aseptic precautions, 

 with portions of a tubercular organ, e.g., the spleen. The portions of 

 tissue should be fairly large, and should be well rubbed into the broken 

 surface of the medium. Cultures may, however, be obtained from sputum 

 by means of antiformin, as this substance readily kills most of the ordin- 

 ary bacteria and has comparatively slight effect on the tubercle bacillus. 

 Antiformin sjiould be allowed to act on sputum in the proportion and for 

 the time mentioned in paragraph (1), the mixture should then be eentri- 

 fuged, the supernatant fluid removed, and the deposit washed with sterile 

 water and again eentrifuged, these processes being repeated several times. 

 If, then, inoculations be made from the deposit on blood serum or on 

 Dorset's egg medium and glycerin egg medium, pure cultures of the 

 tubercle bacillus may, in some instances, be obtained. The method is one 

 which gives good results. 



