620 PATHOGENIC MICROORGANISMS 



LEPROSY BACILLUS LEPR^E 



The bacillus of leprosy was first seen and interpreted as the 

 etiological factor in the disease in 1879, by G. Arrnauer Hansen, g 

 a Norwegian observer. Hansen found the bacilli in the tissues of the 

 nodular lesions of patients, lying in small clumps, intra- and extra- 

 cellularly, as well as in the serum oozing from the tissue during its 

 removal. Hansen's observation was the fruit of over six years of careful 

 study and as to his priority in making this discovery, there can be 

 no doubt. Almost simultaneously with his publication, however, 

 Neisser 9 published similar results, obtained by him during a brief stay 

 at Bergen, during the preceding summer. The bacilli described by 

 these workers are now recognized as being unquestionably the cause of 

 the various forms of the disease known as leprosy. 



Morphology and Staining. The leprosy bacillus is a small rod 

 measuring about 5 to 7 '/* in length and has a close morphological 

 resemblance to Bacillus tuberculosis, except in that it is less apt to dis- 

 play the beaded appearance and is slightly less slender than the latter. 

 It is non-motile, possesses no flagella, and forms no spores. 



Like tubercle bacilli, the leprosjr bacilli belong to the class of 

 so-called acid-fast bacteria, being stained with much difficulty; but 

 when once stained they are tenacious of the color, offering consider- 

 able resistance to the decolorizing action of acids. It is necessary 

 for differential diagnosis, however, to note that both the difficulty of 

 staining and the resistance to decolorization are less marked in the case 

 of this microorganism than in the case of Bacillus tuberculosis. It was 

 this peculiar behavior to stains that caused the delay of several years in 

 Hansen's publications, since he failed in obtaining good morphological 

 specimens until the work of Koch upon bacterial staining had supplied 

 him with proper methods. The bacillus is stained most easily with 

 anilin-water-gentian-violet or with carbol-fuchsin solution. Stained by 

 Gram's method, it is not decolorized and appears a deep blue. Differ- 

 ential staining by the Ziehl-Neelson method shows the bacillus stained 

 red unless decolorization by means of the acid and alcohol are prolonged 

 for an unusual time. A differentiation from tubercle bacilli by virtue of 

 greater ease of decolorization is of value only in the hands of those 

 having much experience with these bacilli, and follows no regular laws 



8 Hansen, Virch. Arch., 79, 1879. 



9 Neisser, Breslauer arztl. Zeitschr., 20, 1879. 



