1870.] 



on the Human Economy. 



523 



The bulk of die lungs remaining the same in the tropics as in colder lati- 

 tudes, or being even somewhat diminished from their comparative abeyance 

 as excreting and heat-generating organs, the blood, diverted to the func- 

 tionally excited and congested skin and liver, permits the ingress of a 

 larger quantity of air into the pulmonary air-cells and tubes ; whereas in 

 colder latitudes this is reversed, the lungs being more and the skin and 

 liver less active ; the blood drawn from the latter to the former dimi- 

 nishes the calibre of the air-vesicles and bronchi, lessening the quantity 

 of contained air, as happens to a still greater extent in some lung-diseases, 

 e. g. bronchitis, pneumonia, pulmonary congestion *, and phthisis, tu- 

 bercle and not blood being in the latter the displacing agent. Briefly, the 

 lungs (identical in size in both) contain less blood and more air in tropical 

 than in temperate climates. The truth of the above explanation appears to 

 be confirmed by facts noticeable in Table I., viz. that it is in thoroughly 

 warm tropical regions, where the skin acts most freely and the sensible 

 perspiration is most abundant, that the greatest difference is observable in 

 the capacity of the lungs for air. Thus the difference between the capacity 

 near the equator (temp. 83° F.) and September in England (temp. 65° F.) 

 was 26 cubic inches ; while between the latter and the winter of England 

 (February, temp. 42° F.), when the functions of the skin were much more 

 in abeyance, was no more than six cubic inches. And it corresponds with 

 what Dr. Francis (Bengal Army) f has observed, viz. that the lungs are 

 lighter after death in Europeans in India than the European standard. 

 Parkes has made the same observation, and remarks that it shows appa- 

 rently a diminished respiratory function. 



A knowledge of this law, in addition to its diagnostic value, is evidently 

 of considerable therapeutic importance as furnishing a guide to the rational 

 treatment of many, and especially congestive or inflammatory diseases of 

 the lungs. By its facts the true rationale of the benefit derived in the 

 earlier stages of phthisis, or where it is merely imminent from a sojourn 

 in a subtropical climate, is of easy explanation. Residence in a warm 

 atmosphere is followed by a decrease in the quantity of blood in the affected 

 lungs, by diminished activity in the vital processes carried on therein, by 

 facilitated respiration, and, above all, by diminished lung-work from vica- 

 rious action of the physiologically excited skin and liver ; while the in- 

 halation of milder, more equable, and less irritant air diminishes the 

 chances of excitement or increase of distressing local inflammation and 



descent of the diaphragm ; and the exceptional case above related of diminution of the 

 costal circumference may possibly be explained by the diaphragm counteracting the 

 other respiratory muscles, whilst unusually contracting in answer to the room required 

 by this reserved power of the bases of the lungs being called into action. 



* See an admirable letter on " Swimmer's Cramp " in the 'Lancet for October 9 » 

 1869, p. 531, by my friend Mr. Henry Hales of Eeigate, who first suggested to me a 

 satisfactory explanation of the above phenomena. 



t Parkes, 1 Practical Hygiene,' 2nd edit. p. 463. 



