366 A MANUAL OF BACTERIOLOGY 



(7) In the tissues the glanders bacillus is difficult to demon- 

 strate. Sections may be stained for half an hour with carbol 

 methylene-blue, treated with 4 per cent, acetic for a few seconds, 

 washed, and rapidly dehydrated with alcohol, cleared and mounted. 

 McFadyean recommends, after treating with acetic and washing, 

 flooding with a saturated solution of tannic acid in water for 

 fifteen minutes, washing, counter-staining in a 1 per cent, aqueous 

 solution of acid fuchsin for fifteen to thirty seconds, washing, 

 dehydrating, and clearing in cedar oil. 



" Acid-fast " Bacilli 



An important characteristic of the tubercle, leprosy, smegma, 

 and certain other bacilli is the property they possess when stained 

 with fuchsin of retaining the red colour after treatment with a 

 strong solution of a mineral acid (25 per cent, sulphuric or 30 per 

 cent, nitric). They are therefore termed " acid -fast." Most 

 other organisms are rapidly decolorised even by 1 or 2 per cent, 

 sulphuric acid, but it must be recognised that several apparently 

 saprophytic bacilli are also " acid -fast." This property of " acid- 

 fastness " is due to fatty or waxy substances within the bacilli 

 (see p. 375), and it is stated that cultivation of certain saprophytic 

 organisms in media containing butter converts them into acid- 

 fast forms. 



" Acid-fast " bacilli are also present in Johne's disease, occa- 

 sionally in rats, in butter (Petri, Kabinowitsch, Eubner), on 

 certain Graminaceae (the " Timothy-grass bacillus " of Moeller), 

 and in dung (the "Mist bacillus"). It has been suggested that 

 these saprophytic acid-fast bacilli may be derived from the 

 tubercle bacillus, but Panisset's work gives no confirmation of 

 this. 



The Streptotrichese occasionally exhibit " acid-fast " proper- 

 ties. All the acid-fast bacilli seem to be Gram -positive. 



Tuberculosis 



Tuberculosis is a disease which attacks man and many 

 of his domestic animals, and wild animals in a state of 

 captivity may become infected. 



The conception of tuberculosis was originally an 



