This story of pathology influencing racial qualities is not new in the history of the world. It is not improbable that even certain periods of decadence in Egyptian history which have ordinarily been attributed to the so-called running out of particular ruling races or families, or to the degeneration of the people consequent upon luxury, were really the result of the spread of the hook-worm disease through certain portions of Egypt. Dr. Sandwith, who has studied the disease very carefully in Egypt, is sure that it has existed there for at least four thousand years, and that the descriptions of certain affections which occurred in Egypt in historic times were really due to the same cause as now is known to produce the so-called Egyptian chlorosis, the name that was used for hook-worm disease in Egypt. Workers in soil, and in mines and in tunnels, are especially likely to be affected by it, and whenever it is neglected it spreads rather widely, as is seen in the mines of Germany and Hungary at the present time. As the cause was unrecognized in the olden time, it is possible that periods of supposed lassitude among the people were really due to infection by this parasite. _Malaria and Degeneration_.--In recent years it has come to be generally recognized that the decadence of Greece, for instance, was not due to moral causes so much, perhaps, as to physical reasons. During the classic periods in Greece there are no traces of malaria. After the invasion of Sicily, the expedition against Syracuse and other attempts on the part of the cities of Greece to spread their dominion, malaria seems to have been introduced among her people, and as the _anopheles_ mosquito was already there, the malaria spread widely, and in the course of a century affected so many of the people that their energy and ambition and initiative were to a great extent destroyed. {108} It is well known that these effects often occur as a consequence of malaria, and as generation after generation is affected by the disease, are emphasized more and more. The relaxing effect of tropical climates, of which we have heard so much, and which is supposed after a time to bring about the inevitable production of a race eminently lazy and careless of the future, is probably much more due to certain affections, such as malaria and those consequent upon animal parasites, than to any constitutional change that has taken place in the body, or any profound corresponding change in the mind. It is a case of the body influencing the mind and producing an apparently different race from that which existed before, though all this may be changed for the better by some even slight amelioration of bodily conditions.