Tropical medicine varies according to the part of the world in which it is located. The American tropics, the African tropics, and the Asiatic tropics have a few diseases in common, but many entities are peculiar to or prevalent in one part of the world and not in the others. This very well-known fact influences the pathology of separate areas of the world so much so that the expression tropical medicine must be accompanied by an explanation of the part of the tropics in which it is studied. Furthermore, the conditions which are common in some countries of the same continent are not prevalent or even present in another, and, more precisely, conditions prevalent in rural areas cannot be found in the cities of the same country. For instance, if one were to look for pinta (mal del pinto) in Mexico City, it would