1892.] MICKOSCOriCAL JOURNAL. 171 



of l)acilli is concerned. This is due to the fact that chniips of 

 sputum that usually contain a larger number of tubercle-bacilli 

 than the more liquid portion are so deeply stained as to obliterate 

 their jDresence. In order to reduce the sputum to a more homo- 

 geneous consistence and at the same time to concentrate into a 

 small mass the bacilli in a large quantity of sputum, Biedert 

 mixed the sputum with twice its volume of a 3 per cent, solution 

 of caustic potash or soda (soda being preferred) and boiled the 

 mixture until perfectly fluid, after which it was placed in a conical 

 glass and allowed to stand until a sediment had formed. Upon 

 decanting the supernatant liquid, tubercle-bacilli otherwise 

 difhcultor impossible to find were readily discovered in stained 

 cover-glass preparations made from the sediment in the bottom of 

 the vessel. In a recent article, (-) Biedert again dwells on the 

 value of this method. Although the process requires considerable 

 time, the advantage to be gained by concentrating the tubercle- 

 bacilli in a large quantity of sputum into a small sediment is 

 obvious. This is also a convenient method for preserving sputum 

 for subsequent examinations, as the bacteria remain unchanged 

 for a considerable time. 



Among the various pi'ocesses that have been proposed and 

 which are based upon the principles set forth by Biedert, the fol- 

 lowing may be mentioned : 



Kaatzer (^) employed from a i to 3 per cent, solution of caustic 

 soda or potash, which dissolved the cells, mucus, etc., but pre- 

 served the elastic fibers and bacteria. Cover-glass prepaiations 

 were made from the sediment. He also employed a dilute solu- 

 tion of acetic acid to clear the preparations. 



Kiihne (^) added an equal volume of a saturated aqueous solu- 

 tion of borax to the sputum in order to overcome its viscidity and 

 to obtain a thin even layer on the cover-glass. This mixture re- 

 mained good for several weeks. Putrefaction is prevented and 

 the tubercle-bacilli continue to stain nicely. He also used for 

 less viscid sputum a concentrated aqueous solution of ammonium 

 carbonate. Kuhne also dwells upon the importance of estimating 

 the number of tubercle-bacilli present. 



Miihlhiiuser (5) does not advise the use of stronger solutions 

 of caustic potash than 2 per cent. He differs from Biedert in 

 taking a smaller quantity of the sputum and adding from six to 

 eight times its volume of the potash solution. 



Gabbet's Staining Process. (") — This method was found 

 to be very convenient and quite satisfactory in staining'the tuber- 

 cle-bacilli both in cover-glass preparations and in sections of tu- 

 berculous tissue. The stain is practically the same as that used 

 in Ziehl-Neelsen's method, but the acid is combined with the 



2. Ibid., 1891, No. 2, p. 31. 



Kaatzer, P.: Wood's Monographs, V, 1890, p. 97. 



Kuhne, H.: Centralblatt f. Bakteriologie u. Parasitenkunde, viii. 1890, p. 293. 



5. Muhlhauser, H.: Deutsche med. Wochenschrift, 1891, No. 7, p. 282. 



6. Kahlden, C. v: Technik der histologischen Untersuchung, etc., Jena, 1890, p. 59. 



