318 BACTERIA PATHOGENIC TO MAN 



differing slightly from the tubercle bacillus in the ease with which they 

 take up the ordinary aniline dyes, they behave like tubercle bacilli in 

 retaining their color when subsequently treated with strong solutions 

 of the mineral acids and alcohol. The slight difference in staining 

 characteristics is too little to be relied upon for diagnostic purposes. 



Biological Characters. Attempts to cultivate the bacillus leprse have 

 been frequently made, but so far with negative results. 



Pathogenesis. Numerous inoculation experiments have been made 

 on animals with portions of leprous tubercles, but there is no conclusive 

 evidence that leprosy can be transmitted to the lower animals by inocu- 

 lation. The inference that this bacillus bears an etiological relation 

 to the disease with which it is associated is based entirely upon the 

 demonstration of its constant presence in leprous tissues (Fig. 99). 



FIG. 99 



Leprosy bacilli in nodule. (Kolle and Wassermann.) 



The bacilli are found in all the diseased parts, and usually in large 

 numbers, especially in tubercles on the skin, in the conjunctiva and 

 cornea, the mucous membranes of the mouth, gums, and larynx, 

 and in the interstitial processes of the nerves, testicles, spleen, liver, 

 and kidneys. The rods lie almost exclusively within the peculiar round 

 or oval cells of the granulation tissue which composes the leprous 

 tubercles, either irregularly scattered or arranged parallel to one another. 

 In old centres of infection the leprosy cells containing the bacilli are 

 larger and often polynuclear. Giant cells, such as are found in tuber- 

 culosis, are claimed to have been observed by a few investigators (Boinet 

 and Borrel). In the interior of the skin tubercles, the hair follicles, 

 sebaceous and sweat-glands are often attacked, and bacilli have some- 

 times been found in these (Unna, etc.). Quite young eruptions often 

 contain a few bacilli. A true caseation of the tubercles does not occur, 

 but ulceration results. 



In the anaesthetic forms of leprosy the bacilli are found most commonly 

 in the nerves and less frequently in the skin. They have been demon- 



