206 BACTERIOLOGY 



balsam in the ordinary way, and examined under the micro- 

 scope. The stained bacilli are decolorised at once by 

 treatment with glacial acetic acid ; other acids take longer. 



A better method than Lustgarten's is that described by 

 De Giacomi, in which the preparations are treated with 

 solution of iron perchloride after being stained in Ehrlich's 

 solution of fuchsine in aniline water. Lewy recommends 

 staining in carbolic fuchsine and decolorising with distilled 

 water as the surest and most convenient method. That of 

 Doutrelepont and Schiitz consists in staining the pre- 

 parations for twenty-four hours in a one per cent, solution 

 of methyl violet and decolorising for some seconds in dilute 

 nitric acid, after which they are transferred for ten minutes 

 to alcohol of about sixty per cent, strength. The sections 

 are then double- stained by leaving them for a few minutes 

 in a watery solution of safranine, and are thoroughly washed 

 in sixty per cent, alcohol. By this process the bacilli appear 

 blue and the nuclei and tissue light red. 



Marschalko recommends staining the sections of 

 syphilitic tissue and cover-glass preparations of syphilitic 

 secretion in Loffler's methyl blue for three to four hours at 

 incubation temperature, or twelve to twenty-four at that of 

 an ordinary room, washing in water, and double-staining 

 for one to five minutes' in concentrated aqueous solution of 

 vesuvine. 1 



Bacillus tuberculosis. Tuberculosis was regarded as an 

 infectious disease even by the older physicians ; indeed, 

 this opinion may have preceded the teaching introduced 

 in the course of time by the pathological anatomists (such 

 as Virchow and Eokitansky), which was restricted to the 

 description of the microscopic and naked-eye appearances 



1 [Some authorities believe this to be identical with a bacillus found in 

 normal smegma praeputiale, &c., which has a similar appearance and similar 

 peculiarities of staining. The latter is said, however, not to stain by 

 Doutrelepont's method.] TB. 



