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



15*4 in the West Indies winter season (temperature 79° to 83°, shade) ; 

 while, again, the sick-bay man's were 17*3 in England during winter, and 

 16 in the West Indies, my own were 17'5 in England, and 16*2 in the 

 West Indies. The same may be noticed in an artificial climate of a heated 

 room in England. Thus, while my respirations out of doors in a tempera- 

 ture of 30° F. were 17*5 per minute, they rose to 15*8 shortly afterwards 

 by simply standing before a fire in a temperature of 57° F. 



From these data we find that the increased quantity of air and oxygen 

 inspired in the tropics does not make up for the diminished number of 

 respirations in supplying the same amount of air and oxygen for blood- 

 purification as in cold climates, though doubtless a requisite quantity is 

 inspired, less probably being needed there, as will presently appear, to 

 carry on the vital processes. Thus, taking the average number of respi- 

 rations in the temperate climate of England at 17 (Table Y.), and the 

 quantity of air inspired each breath at 15 cubic inches, this would give 

 255 cubic inches per minute. Now if the chest (Table I.) gains in capacity 

 by an average of 31 cubic inches ( = 12' 24 per cent.) in the tropics, the 

 gain on each ordinary respiration would be 1*836 cubic inch, thus raising 

 the quantity inspired each breath to 16*836 cubic inches. The average 

 number of respirations being taken at 14, this would give 235*704 cubic 

 inches per minute, i. e. less by 19 cubic inches (8 per cent.) than in tem- 

 perate climates ; equal to 1157*760 cubic inches per hour, or 27786*24 

 cubic inches per day. Thus — 



Cubic inches Number Cubic inches 

 in each of respi- respired per 



inspiration. rations. minute. 



England 15 x 17 = 255 



Tropics 16*836 x 14 = 235*704 



Difference in favour of a temperate climate 19*296 cub. in. (=7'567p.c.) 



This decrease of 7*567 per cent, in the quantity of air respired daily 

 diminishes the quantity of carbon which the lungs in ordinary circumstances 

 can throw off in the tropics by 0'7oQ7 oz., or rather more than | oz. ; 10 

 ozs. being taken as the average amount thrown off in temperate climates*, 

 will give 9 243 oz. as the amount for the tropics. But as tropic air con- 

 tains less oxygen for a given bulk than air of colder latitudes, according to 

 Dalton and Gay Lussac's law of expansion of gases by heat, the decarbo- 

 nizing capabilites of the lungs in tropical latitudes will evidently be still 

 further curtailed, and the amount of carbon they can throw off con- 

 siderably decreased. Air increases by its volume for every Fahrenheit 

 degree of heat ; and the difference between the temperatures in which these 

 experiments were carried on being 18° F. (65° and 83° F.), if we reduce 

 the amount inspired in the tropics by a -y 1 -- part, this will give its equiva- 

 lent bulk in the temperate zone. Thus, — 



* Hooper, 1 Physicians' Tade Mecum.' Mean of three estimates by LaYoisier and 

 Seguin, Davy, and Allen and Pepys. 



