THE INFLUENCE OF THE ENVIRONMENT UPON MAN 336
(1) Among men there is no normal environment. (2) The effect of
exercise, (3) of general conditions, (4) and of climate. (5)
Huntington’s theory of optimum climatic conditions. (6) The
effect of food, altitude, &c. (7) Statistical results. (8)
Effect of disease. (9) Evidence derived from twins. (10)
Conclusion that modifications, with the exception of those
produced by disease, are not of great importance, though of more
importance than in the case of species closely allied to man.