405 
of skin, nevertheless, and is of frequent occurrence ; while in Europe 
such a lesion is so rare as to be a curiosity. 
In considering a probable explanation of this phenomenon, we 
must note that even among negroes the frambesial eruption is rarely 
seen in towns, and while it is common in some West Indian islands, 
it is rare or absent from others. 
I have already suggested that damp, hot places in the tropics, 
with dense vegetation, show a prevalence of yaws. This, I think, 
will be found a rule. Numa Rat states that yaws is absent from 
Anguilla, 1 which is flat, dry and barren. The typical yaws district is 
a deep valley or ravine in a tropical volcanic island, where vegetation 
is rank and the rainfall high. 
Yaws is, therefore, very prevalent in Dominica, St. Vincent, 
St. Lucia and Grenada. It occurs to a less extent in Antigua, 
St. Kitts and Nevis. Antigua is flat and not wooded, except at one 
part. St. Kitts and Nevis, though lofty and volcanic, have long 
slopes sweeping away to the sea. The land here is cleared and 
cultivated. There are a few bushy ravines with villages, and in these 
yaws may be found. 
There is, then, another factor besides the character of the skin 
which determines the appearance of frambesiae. We cannot yet 
predicate this factor, any more than we can explain many other 
examples of the variability of syphilis. Why, for instance, does 
hpoid ulceration of the face happen so frequently on the Windward 
side of St. Vincent, while destructive rhinopharyngitis is the rule on 
the Leeward side? Why do some patients get a formative 
periostitis, and others necrosis of bone ? 1 may be allowed to copy 
from a recent letter of mine 2 : —“ To understand this protean disease, 
w e must realise that various factors intervene to determine its 
manifestations. We can appreciate some of these. T he races and 
individuals who tax their nerve system suffer from nerve syphilis, 
u hich is comparatively rare among negroes. The negro, with his 
highly-specialised and active skin, displays an exuberance of 
eru ptions rarely seen in Europe. The labourer, exposed to injuries, 
develops grave bone lesions. The women in St. Kitts, who 
L Re Port on Anguilla. Colonial Reprints, No. 20. 
Journal of Tropical Medicine, May 15th, 1906. 
