522 



Dr. Rattray on the effects of Change of Climate [June 16, 



whereas here they are diminished in numher. To increase the one and 

 diminish the other, the first implying augmented, and the second decreased 

 energy in the respiratory muscles, implies an anomaly which it is un- 

 necessary to accept when the phenomena can be otherwise and better 

 explained. 



2. External measurement, moreover, shows that there is actual increase 

 in the capacity of the chest from its expansion by increased action by its 

 inspiratory muscles. Thus in three adults in which the chest was mea- 

 sured by the spirometer and tape in the winter of England (average tem- 

 perature 30~-32 c F.), and again at Lisbon* (average temperature 60° F.), 

 though in all three there was a decided increase in the capacity of the 

 lungs for air to an average of 1 1 cubic inches, there was no perceptible 

 increase in the circumference of the chest. In one case the latter had 

 apparently decreased by one inch, as if from loss of muscular tone. 



3. It is more than doubtful if the system actually requires an increased 

 quantity of air or as much oxygen to carry on the vital processes in the 

 tropics as in cold climates, and the above-mentioned data prove that it 

 actually gets less of both. Less oxygen is required in the high tempera- 

 tures of low latitudes, because the tissues generally decay less rapidly*. 

 Owing to diminished mental and bodily exertion of the two which make up 

 the bulk of the body, viz. the muscular and nervous, less is required for 

 the metamorphosis of waste particles. Where a diminished necessity and 

 desire for food lessen the ingesta, and judicious selection reduces the 

 amount of carbon this contains, less oxygen is required for direct combina- 

 tion with the elements of the food to generate heat. Moreover it is certain 

 that the increased absorption of oxygen by the functionally excited skin in 

 the tropics, where it acts vicariously for the lungs as a respiratory organ, 

 lessens materially the amount 'required by the lungs. Furthermore, the 

 skin is aided in relieving the lungs in the decarbonizing process by the 

 functionally excited liver and perhaps kidneys, which throw off the carbon 

 in forms which do not require much oxygen for their formation, viz. as 

 bile and uric acid. 



The true explanation appears to be that there is really no actual in- 

 crease in the capacity or size of the chest and enclosed lungs, but only an 

 alteration in the relative proportion of blood and air contained in the latterf. 



♦Carpenter and others doubt this, and believe that they decay more rapidly; in 

 other words, that when used there is a greater waste for the same amount of work. 

 The sum total of this, however, for all the tissues will probably not be greater than the 

 reduction due to the diminished amount of work which the principal tissues hare to 

 perform. 



t With regard to the observation that the increased capacity for air in the chest is 

 11 only an alteration in the relative proportion of blood and air in the lungs," there 

 must be a reservation made in favour of a statement (though it still, perhaps, has to 

 be proved) that the bases of the lungs have a reserved capacity for air, any enlarge- 

 ment of which would, of course, have to be measured, not by expansion of the costal 

 walls, but by protuberance of the abdomen, through encroachment on its cavity by 



