220 TROPICAL MEDICINE AND HYGIENE 



from S. pallida has been found by Castellani in yaws, 

 5. pertemiis. That the diseases belong to the same class 

 is clear; that they are identical is a different matter, and 

 is open to serious question. 



The manifestations of yaws for at least the first three 

 years of the disease are all of the same character, the 

 primary sore and each successive eruption differing 

 slightly in moist parts, or when under thickened epi- 

 dermis. Syphilitic cutaneous manifestations are poly- 

 morphic. Yaws may be universal in a population, but 

 if uninfected newcomers of any race Europeans, Portu- 

 guese, Chinese, Negro, Malays, Indians are introduced 

 into such a community and are infected, the disease they 

 acquire is yaws, and resembles in all its characters the 

 disease in the native population. From a single source 

 of infection in a negro the disease has been acquired in 

 the same form in a whole family of Portuguese, and in 

 an Indian servant. Yaws therefore breeds true. 



Syphilis, when acquired by members of the same races, 

 presents the usual characters of that disease. Syphilis is 

 little modified in persons resident in the Tropics. The 

 formation of gummata and the extensive and destructive 

 bone lesions do not occur in yaws. It is sometimes urged 

 by those with little experience of some of the native races, 

 amongst whom the disease is common, that the over- 

 crowding and filth of the native houses favour the wide 

 diffusion of the disease, and that therefore the fact that 

 all the children have " yaws " is no argument against the 

 disease being syphilis. A closer study of these races will 

 convince anyone that as regards personal cleanliness and 

 absence of overcrowding and morals they compare very 

 favourably with the lower classes of Europeans, amongst 

 whom syphilis does not become universal in the children. 



Yaws does not protect from syphilis nor syphilis from 

 yaws. The relationship between yaws and syphilis, in the 

 sense of both diseases being due to organisms of the 

 same genera, is admitted and was predicted, but the 



