254 LEPROSY. 



with the fact, to be afterwards stated, that the bacilli arc 

 present in fewer numbers. 



Bacillus of Leprosy. This bacillus was first observed 

 in leprous tissues by Hansen in 1871, and was the subject 

 of several communications by him in 1874 and later. 

 Further researches, first by Neisser in 1879, and afterwards 

 by observers in various parts of the world, agreed in their 

 main results, and confirmed the accuracy of Hansen's 

 observations. The bacilli as seen in scrapings of ulcerated 

 leprous nodules, or in sections, have the following characters. 

 They are thin rods of practically the same size as tubercle 

 bacilli, which they also resemble both in appearance and 

 in staining reaction. They are straight or slightly curved, 

 and usually occur singly, or two may be attached end to 

 end ; but they do not form chains. When stained they may 

 have a uniform appearance, or the protoplasm may be 

 fragmented, so that they appear like short rows of cocci 

 darkly stained alternating with unstained points. They 

 often appear tapered at one or both extremities ; occasion- 

 ally there is small club -like swelling. Bacilli, partially 

 broken down, are also seen. They take up the basic 

 aniline stains rather more readily than tubercle bacilli, but 

 in order to stain them deeply a powerful stain, such as 

 carbol-fuchsin, is necessary. When stained, they strongly 

 resist decolorising, though they are more easily decolorised 

 than tubercle bacilli. The best method is to stain with 

 carbol-fuchsin as for tubercle bacilli, but to use a weaker 

 solution of sulphuric acid, say 5 per cent, in decolorising ; 

 in the case of films and thin sections, decolorising with 

 such a solution for fifteen seconds is usually sufficient. 

 Thereafter the tissues are coloured by a contrast stain, such 

 as a watery solution of methylene-blue (vide p. 102). The 

 bacilli are also readily stained by Gram's method. Re- 

 garding the presence of spores practically nothing is known, 

 though some of the unstained or stained points may be of 

 this nature. We have, however, no means of testing their 

 powers of resistance. Leprosy bacilli are non-motile. 



Position of the Bacilli. They occur in enormous num- 



