539 
by an increase of malaria. The change in the Greek character was 
just that which we should expect malaria to produce in a highly 
sensitive and cultivated people, while the savage brutality of the later 
Romans may be due to the same cause. The peculiar effects of a 
disease on national morality will certainly vary with the prominent 
national characteristics. The more effeminate Greek grew weak 
and inefficient ; the stern Roman became viciously cruel. But it 
must always be carefully remembered that other factors, physical and 
psychological, contributed to the change in both cases. The growth 
of intelligence, resulting in dissatisfaction with existing institutions; 
the decay of agriculture or trade ; the slow effects of vice and luxury ; 
the exhaustion of the conditions which stimulate a people to aspire to 
national greatness all these were doubtless important factors in the 
decline of Greece and Rome. But malaria gave rise to physical 
conditions which afforded an excellent opportunity for other influences 
to produce their full effect. It must also be remembered that these 
conditions would be reproduced from generation to generation, for 
malaria was continuously present, apparently increasing until nearly 
everybody was more or less infected. A temporary disaster, whether 
it be war or a virulent epidemic, often stimulates to great deeds and 
heroic actions; but a weakening endemic disease, attacking every 
fresh generation as it is born, gives the nation which is its victim 
no chance to recuperate. 
In the preceding pages 1 have indicated very briefly the main 
conclusions which it seems just to draw from a study of the classical 
literatures. But only the fringe of the subject has been touched, 
even within the limited area to which I have confined my own investi¬ 
gations, and a vast field remains to be worked by those who will take 
the trouble to trace the effects of malaria upon other nations. It is 
only from a comparison of results obtained in a series of enquiries 
that any really valuable knowledge can be expected. The influence 
of diseases other than malaria is also most important, and should be 
carefully studied. Mr. T. Spencer Jerome, who has for many years 
Paid attention to the biological aspect of history, sends at my request 
the following note on the transformation of the Roman character. 
The remark it contains about pestilence killing off those o t e 
greatest nerve force is interesting, as it is just possible that the great 
Athenian plague of 430 B.C. weakened the general health by attack- 
