1872.] change of Climate on the Human Economy. 



Table III. shows that, as with latitude, change of altitude, 

 i. e. temperature, causes a rise and fall in the spirometric measurement. 



Place &c. 



Spirometric measure- 

 ment of lungs. 



.Aug. 14. Level of Sea. Temp. 75 F. ... 



A. E., get. 40. 



Ascension. \ Aug. 14. Green Mountain Temp. 67°F. ... 

 Lat. 8°S. (2000 feet high). 



1 Aug. 15. „ Temp. 65 F. ... 



cubic inches. 

 266 



249 

 243 



This gives a difference of 18 cubic inches from a 10° F. reduction of 

 temperature. Summer heat and winter cold in temperate latitudes, and 

 also the atmosphere of artificially heated or cooled rooms or wards, have 

 corresponding results. 



That this spirometric law of climate has little except perhaps a secon- 

 dary and minor connexion with an increase or decrease in the capacity 

 of the bony chest is shown : — 



1st. By the usual absence of any change in the circumference of the 

 adult chest when the rise and fall are greatest (Table I., cases 1 and 2). 



2nd. By the slight interference of growth of chest with the manifes- 

 tations of the law, both in the adult (Table I., cases 3 and 4), and 

 especially the cadets (Table II., cases 1 to 47) and junior officers 

 (Table II., cases 48 to 60). 



The spirometric measurement of the lungs is probably occasionally in- 

 creased by actual chest expansion when an increased respiratory function 

 is suddenly required in health or disease. But this is exceptional ; and 

 in emergencies, in cold and warm climates alike, this result is usually 

 effected in a more natural and easier way, viz. by increasing the frequency 

 of the respiration. 



The only theory that will satisfactorily explain this tropical increase in 

 the spirometric measurement of the lungs, with its peculiarities, and 

 correlate it with other apparently opposed respiratory phenomena, such 

 as slower and gentler inspiration, and also the post mortem lightness of 

 the lungs observed by Francis and Parkes, is that it arises not from en- 

 largement of the chest, but merely from a change in the relative quantity 

 of blood and air in the lungs. The law of the lungs is merely a sequel 

 of the greater law of the circulation, by which the entire blood-current 

 is redistributed, and either attracted surfaceward by heat or driven 

 inward by cold. The lungs, unaltered in size, contain less blood, actually 

 and relatively, and more air in the tropics ; they are less vascular, but 

 more inflated. The oscillation in the relative proportion of blood and 

 air follows an inverse ratio, the one rising, for an obAdous reason, as the 

 other falls. It is the rise or fall in the air, and not in the blood, which 

 corresponds with the rise and fall of temperature. Blood is the dis- 



