ETIOLOGY 



and common in the West Indies. In South America it appears to 

 be common in Colombia, Venezuela, the Guianas, and Brazil, but 

 whether it is rare or simply not recognized in other countries is 

 unknown. 



It appears to be spread all through Africa, but is certainly rare 

 in West Africa, more common in Central and East Africa, and 

 decidedly more common in North and in South Africa, where there 

 is the celebrated Robbin Island Leper Asylum. There are people 

 who believe Egypt to be the original home of the disease, from 

 whence it spread to Asia and Europe. 



etiology. — The disease is caused by Hansen's bacillus, which 

 morphologically has the greatest resemblance to the tubercular 

 bacillus, and is stained by the same methods. 



With regard to the cultivation of the bacillus there are three 

 views : — 



1. That it has never been cultivated. 



2. That it can be cultivated as a streptothrix or nocardia. 



3. That it can be cultivated as a bacillus. 



1. That it has never been cultivated. — This is still the most 

 generally accepted view. 



2. That it can he cultivated as a Streptothrix. — This is the view 

 held by Bordoni-Uffreduzzi, Babes, Rost, Kedrowsky, Shiga, Hew- 

 lett, Bayon, Johnston, and others. They maintain that Hansen's 

 bacillus in cultures becomes a filamentary branching non-acid- 

 resisting organism, which, when injected persistently into animals, 

 produces the signs of leprosy. From these animals, they say, it can 

 be recovered as an acid-resisting bacillus. The strain separated by 

 Kedrowsky, and further investigated by Bayon, is the one which in 

 our opinion is the most important with a view to further researches. 

 The growth of the germ is slow, and the colonies coalesce into a 

 whitish mass. The inoculation of cultures into monkeys, rats, and 

 guinea-pigs, gives rise, according to Bayon, to leprosy- like lesions, 

 with very little tissue proliferation, no caseation necrosis, no 

 vascular sclerosis, and with presence of numerous acid-fast bacilli. 

 Serological reactions, such as agglutination and complement fixa- 

 tion, are rather in favour of Bayon' s theory. Moreover, the 

 inoculation of an extract of the cultures induces in leprotic patients 

 a reaction with fever, comparable to that induced in tubercular 

 patients by tuberculin. 



In 1915 Eraser and Fletcher were unable to confirm Kedrowsky 

 and Bayon's results, and came to the conclusion that Kedrowsky's 

 bacillus is not the leprosy bacillus. 



3. That it can he cultivated as a Bacillus. — This is the view held 

 by Clegg, Duval, and others. Clegg succeeded in cultivating his 

 bacillus in symbiosis with an amoeba. The cultures are chromo- 

 genic. The inoculation of this germ apparently does not produce 

 leprotic lesions. Duval gives importance to a non-chromogenic 

 always acid-fast bacillus he has isolated, which grows very slowly, 



