ENVIEONMENT AMONG MEN 345 



injurious mental disturbances. What is remarkable is that the 

 optimum conditions for negroes should be the same as for 

 Europeans. It will require more proof than has yet been advanced 

 before this can be accepted. Further, the changes in climate 

 which the theory demands have not been proved. Professor 

 Gregory has reviewed the question and his conclusions do not 

 support those of Huntingdon — at any rate not in such a manner 

 as to render the theory tenable.^ Nevertheless, whatever the 

 fate of the theory in its present form may be, its enunciation 

 has raised many interesting questions and has incidentally helped 

 to show how little we know at present regarding the effect of the / 

 surroundings on man. 



6. When men move from one climate to another they come 

 under the influence not only of changes in temperature and 

 moisture but also of food and sometimes of altitude and other 

 factors about the effects of which there is a considerable amount 

 of information. A vegetarian diet is said to produce changes in 

 the gut ; but changes in beverages are probably of far greater 

 importance than changes in food. The effects of alcohol have 

 been closely studied, chiefly with regard to its influence upon 

 nervous tone. Nervous tone is affected in an important manner 

 by many drugs, as for instance by opium, and in a lesser degree 

 by tea and coffee. Changes in nervous tone are of such importance 

 that its susceptibility to various influences has to be borne in 

 mind. It is quite possible that the introduction of a new form of 

 beverage into a country might have a perceptible effect upon 

 the average condition of nervous tone and thus have a bearing 

 upon the course of history. 



Altitude is known to have various effects upon physical 

 characters. The fact that the larger lung capacity of those 

 who live at high altitudes diminishes on descent to the plains, 

 as recorded by Darwin of the Quicha Indians, is evidence that 

 this character is in part at least environmental.^ The effect of 

 high altitudes has lately been studied in much detail. It is 

 known that there is among other changes an increase in the 

 number of red blood-corpuscles in the blood. ^ 



* Gregory, Geog. Journ., vol. xliii. There have been many studies of the influ- 

 ence of climate upon temperament. See, for instance, Dexter, Weather Influences. 

 2 Darwin, Descent of Man, p. 35. » Acton and Harvey, ' Increase in the 



Number of Erythrocytes ', Biometrika, vol. viii. See also the results of the 

 Monte Rosa and Pike's Peaks Expeditions, Phil. Trans., vols, cciii and ccvi. 



