312 Tuberculosis 



this, more stain should now and then be added. The stain- 

 ing is complete in from three to five minutes, after which 

 the specimen is washed off with water, and then with a 3 

 per cent, solution of hydrochloric acid in 70 per cent, alco- 

 hol, 25 per cent, aqueous sulphuric, or 33 per cent, aqueous 

 nitric acid solution dropped upon it for thirty seconds, or 

 until the red color is just extinguished. The acid is care- 

 fully washed off with water, the specimen dried and mounted 

 in Canada balsam. Nothing will be colored except the 

 tubercle bacilli, which appear red. 



GabbeVs Method. Gabbet modified the method by 

 adding a little methylene-blue to the acid solution, which 

 he makes according to this formula: 



Methylene-blue 2 



Sulphuric acid 25 



Water 75 



In Gabbet's method, after staining with carbol-fuchsin 

 the specimen is washed with water, acted upon by the 

 methylene-blue solution for thirty seconds, washed again 

 with water ilntil only a very faint blue remains, dried, and 

 finally mounted in Canada balsam. The tubercle bacilli are 

 colored red; the pus-corpuscles, epithelial cells, and un- 

 important bacteria, blue. 



In cases in which these methods fail to reveal bacilli 

 whose presence is strongly indicated by the clinical signs, 

 a still more exact method of searching for them is to par- 

 tially digest the sputum with caustic potash, and collect the 

 solid matter with a centrifugal apparatus. When very few 

 bacilli are present in the sputum, this method will often 

 permit them to be demonstrated. When the number is still 

 smaller, it may be possible to show their presence by guinea- 

 pig inoculation when staining methods all fail. 



The possible relation that the number of bacilli in the 

 expectoration of consumptives might bear to the progress 

 of the disease has been investigated by Nuttall.* The total 

 quantity of sputum expectorated in twenty-four hours was 

 received in covered, scrupulously clean conical glasses and 

 measured. The proportion of muco-purulent to fluid matter 

 was noted. Depending upon its viscidity and the number 

 of bacilli present in the sputum, a varying amount of 5 

 per cent, caustic potash solution was added to it (from 



* "Bull, of the Johns Hopkins Hospital," May and June, 1891, 11, 13. 



