34 PHYSICAL INVESTIGATION. PART I.] 



SECTION I. 



ON THE MODE AND MAGNITUDE OF THE PHYSICAL 

 CHANGES TO WHICH MAN IS SUBJECT. 



ALL permanent changes, apart from morbid phenomena, pro- 

 duced on man in the course of time, may, with regard to their 

 origin, be divided into four classes. I. Climate; n. Aliment 

 and mode of life ; in. Psychical influences, growth and decline 

 of mental culture ; iv. Deviation from the original type, result- 

 ing from unknown causes and transmitted more or less per- 

 manently. 



In many cases it cannot with any certainty be determined to 

 which of these four classes certain phenomena belong, and 

 whether they may not be the results of a combination of causes. 

 It is still less possible exactly to ascertain in what manner such 

 causes have produced these changes; which is specially the case 

 with regard to climate. 



What is termed the influence of climate, consists of the direct 

 and indirect influences of the temperature of the air, its degree 

 of moisture, pressure, and chemical composition (malaria) ; the 

 frequency and variations of winds ; rains, their periodicity, etc. 

 Though it is undoubted that a long continuance of such in- 

 fluences produces certain changes in the human organism, but 

 little is known in what mode they are effected. Nothing re- 

 mains then, but to state, as an ultimate fact, the coincidence of 

 climatic influences with certain differences in the corporeal 

 organization. The reason of this uncertainty is, that the effect 

 of the climate cannot easily be separated from that produced by 

 alimentation and mode of living, which generally act in com- 

 bination. It is known that the hygrometric state of the at- 

 mosphere influences respiration and perspiration, and that 

 the absorption of oxygen by the lungs is in inverse proportion 

 to the temperature of the air, and in direct proportion to the 

 barometric state ; it is further known that the barometric state 

 reaches its maximum under 32-33 lat., and is, under the 

 equator, subject to daily regular oscillations ; but all this only 



