YAWS AND SYPHILIS 307 
From a consideration of the clinical, serological, and histological changes 
regarding the two conditions which have been outlined in this chapter, it seems 
obvious that they are closely related. Perhaps in yaws we have a modified virus 
of syphilis, a less virulent one producing a disease that has been modified by 
the portal of entry in many years of successive passage of the virus through the 
epidermis in black-skinned races, and by the habits of life of these people and the 
climate and hygienic conditions under which they live. 
