284 



SCIENCE 



[N. S. Vol. XXXVI. No. 922 



To establish, if possible, an etiological role 

 for any one of the cultures obtained from the 

 human leprous lesion to the exclusion of 

 others, careful comparative studies of the ex- 

 perimentally induced lesion and the serolog- 

 ical tests have been carried out upon a large 

 series of animals. 



In general it may be stated that macroseop- 

 ically the lesions produced in the lower ani- 

 mals do not differ greatly for any of the cul- 

 tures employed, unless it be that the chromo- 

 genic type produces lesions which appear 

 earlier and are more localized. Microscop- 

 ically the cell picture or relation of the ba- 

 cilli to the cells is not sufficiently distinctive 

 of any culture to warrant more than a tenta- 

 tive differentiation. 



In other words the experimental lesions in 

 animals afford no absolute differentiation for 

 any strain of acid-fast organism except of 

 course the tubercle family. Leprous-like 

 lesions are as readily induced experimentally 

 with some of the well-known saprophytic 

 species as they are induced with either the in- 

 fested leprous tissues or with the lepra cul- 

 ture. 



The serological tests with the blood of lepers 

 has not established an etiological role for any 

 type of acid-fast organism recovered from the 

 leprous lesion. The agglutination reaction 

 with the lepers' blood rarely gives a positive 

 reaction in dilution of 1/50 with the sepa- 

 rated Hansen bacilli obtained from the hu- 

 man nodule, while in the majority of cases a 

 reaction is not obtained above a dilution 

 1/10. On the other hand, many of the tubercle 

 family and the acid-fast saprophytes react 

 equally as well and not infrequently in higher 

 dilutions. The complement deviation tests 

 with culture antigen utterly fail to show any- 

 thing specific for the various cultures in so 

 far as the human serum is concerned. How- 

 ever, the serum reaction of animals immun- 

 ized against the various acid-fast species has 

 served to separate into three distinct groups 

 the ehromogenic culture of leprosy (Group I.), 

 the author's non-chromogenic culture of lep- 

 rosy (Group II.) and the ehromogenic sapro- 

 phytic acid-fast species (Group III.). The re- 



action with specific immune sera establishes 

 the fact that there is a difference between the 

 non-chromogenic and the ehromogenic leprosy 

 cultures. Furthermore the serum reaction 

 indicates no relation between these two strains 

 and no relation of either to any known sapro- 

 phytic species. 



SUMMARY AND CONCLUSIONS 



There may be cultivated from the leprous 

 lesion two types of acid-fast bacilli which have 

 distinct characteristics : one an organism 

 which after it has become accustomed to a 

 saprophytic existence produces pigment and 

 becomes extremely pleomorphic; the other a 

 bacillus growing slowly and only upon special 

 media, and retaining always the tinctorial 

 properties of the Hansen bacillus of the tis- 

 sues. Non-acid-fast diphtheroids are occasion- 

 ally encountered in the external lesions, but 

 are perhaps accidental contaminators. 



The acid-fast strain, which subsequently 

 becomes a rapid grower and develops pigment, 

 shows a wide variation in morphology and 

 ability to retain the stain when subjected to 

 decolorizing agents. At times and under cer- 

 tain conditions the individual bacilli are diph- 

 theroid, streptothrical and non-aeid-fast. The 

 slow growing non-chromogenic culture is al- 

 ways acid-fast and can be sharply differen- 

 tiated from the ehromogenic culture by its 

 growth features. 



The animal experiments undertaken for the 

 purpose of differentiating the acid-fast organ- 

 isms recovered from the human leprous lesion 

 and to fix their etiological status are not re- 

 garded as conclusive. 



The serological tests, especially those per- 

 formed with highly immune sera, have proven 

 of some value and suggest that the bacillus of 

 Clegg is not related to any known saprophytic 

 acid-fast ehromogen, and that the non-chromo- 

 genic slow-growing culture from leprosy is 

 different both from Clegg's isolation and 

 from all known species of acid-fast bacilli. 



The role played by the ehromogenic bacillus 

 of Clegg in the production of leprosy is as 

 yet an unsettled question. 



The non-chromogenic strain, while beliav- 



