BACTERIA AND DISEASE 311 



little doubt that leprosy is a bacterial disease produced by 

 the bacillus of Hansen. Bordoni-Uffreduzzi maintains that 

 the parasitic existence of the Bacillus leprce may alternate 

 with a saprophytic stage. This may be of importance in 

 the spread of the disease. There is evidence in support of 

 the non-communicability of the disease by heredity or con- 

 tagion. Segregation does not appear always to result in a 

 decline of the disease, as we should expect if it were purely 

 contagious. Ehlers, of Copenhagen, has, however, as re- 

 cently as 1897, reaffirmed his belief in the contagiousness of 

 leprosy; Virchow, on the other hand, has declared that it is 

 not highly contagious. There is evidence to show that per- 

 sons far advanced in the disease may live in a healthy com- 

 munity and yet not infect their immediate neighbours. 

 Indeed, the transmission of the disease is still an unsolved 

 problem. Mr. Hutchinson suggests diet, particularly un- 

 cooked or putrid fish, as a likely channel; on the other 

 hand, leprosy appears in districts where no fish is eaten. 

 Deficiency of salt, telluric and climatic conditions, racial 

 tendencies, social status, poverty, insanitation, drinking 

 water, even vaccination, have all secured support from 

 various seekers after the true channel by which the bacillus 

 gains entrance to the human body. The real mode of 

 transmission is, however, still unknown. The decline and 

 final extinction of leprosy in the British Islands was prob- 

 ably due in part to the natural tendency of the disease, 

 under favourable hygienic circumstances, to die out, and in 

 part to a general and extensive social improvement in the 

 life of the people, to a complete change in the poor and in- 

 sufficient diet, and to agricultural advancement, improved 

 sanitation, and land drainage. 



At the Leprosy Congress held in Berlin in 1897, Hansen 

 again emphasised his belief that segregation was the cause 

 of the decline of leprosy wherever it had occurred. But 

 there appears to be some evidence to show that leprosy has 



