Mellanby further calls attention to the almost complete absence of rickets in the Island of Lewis in the Hebrides, although the people there live under the most intolerable hygienic conditions. He emphasizes the importance of this fact in support of the view that the disease is essentially due to faulty diet, and not to unfavorable hygienic surroundings.

It is necessary to receive statements about the geographical distribution of rickets with a certain amount of skepticism, since they are often the result of careless observation or of the inability of the observer to recognize mild cases of the disease. The statement is made frequently and accepted generally that rickets does not occur in the tropics or is very rare. As a matter of fact the disease is not at all uncommon in parts at least of Central and South America (Brazil, Venezuela, Guatemala).