1871.] Change of Climate on the Human Economy. 299 



doubtless involves not only the urea and chloride of sodium*, but all of its 

 ordinary ingredients. Both would be far more regular if the system could 

 be kept day by day in strictly similar conditions as to exercise, clothing, 

 draughts, food, and especially drink — a difficult matter at sea, though pos- 

 sible on shore. So that by limiting the drink and increasing it only as 

 thirst prompted, the quantity of urine would keep at a uniform and perhaps 

 healthier standard. The individually different quantities necessary to ac- 

 complish this may be easily ascertained. Thus , allowing 25 oz. free fluid 

 to be what my system requires daily in the average temperature of London 

 (50° F.), the addition of 1 fl. oz. for every degree above, or its deduction 

 for every degree below that, would keep the urine pretty equable, even 

 though its specific gravity and solids might alter (Table IV.). 



Table IV. — To indicate the daily quantity of drink necessary to keep the 

 Urine nearly alike in Temperate and Tropical latitudes. 





30° 



40° 



50° 



GO 



70° 



80° 



90° 





5oz. 



15 oz. 



25 oz. 



35 oz. 



45 oz. 



55 oz. 



65 oz. 



This fact was proved by an experiment (of which Table V. is a synopsis) 

 made in the Pacific in 1 860-6 1, during a passage from Valparaiso (lat. 33° 8.) 

 to Vancouver (lat. 48° N.), when the drink was not kept uniform through- 

 out as in Table III., but increased or decreased, as here indicated, with the 

 desire. 



Table V. — To contrast the Urine at the Equator and North and South 

 Temperate Zones. 





Specific 

 gravity 



of 

 7 cases. 



Quantity 

 in 1 case. 



Avers ge of 7 days furthest south (lat, 33°), temp. 68° F.... 

 ,, „ near equator (lat. 5°), ,, 78° F.... 



furthest north (lat. 53°), „ 58° F.... 



10184- 

 1018f 

 10174 



oz. 

 36 

 45-3 

 44-3 



Here both the quantity and specific gravity increased somewhat ; so that 

 the urine is perhaps not so often or much diminished in the tropics as usually 

 believed. It is so when the drink is stinted, and when, though ample, it is 

 not increased and decreased with the temperature (Table III.) ; but when 

 this is done it remains pretty uniform (Table V.), as it often does even when 

 taken in excess. It is not so much the nephritic as the cutaneous secretion 

 which alters with variations in the amount of drink in the tropics, and in 

 temperate climates the reverse. The functionally excited skin acts- as a 



* Dr. Forbes Watson and Becker, ae quoted in Parkes'i s Practical Hygiene.' 



2 A 2 



