Mr. T. Hopkins's Observations on Malaria. 1 1 1 



be raised to 80° or 90°, evaporation from the body must be- 

 come very feeble. 



In a paper read March 1830, and printed in the 5th vol. 

 of the Society's Transactions, Dr. Dalton has shown that a 

 healthy man taking daily into his stomach 53 ounces of fluid 

 gives off" from the external skin in the same time 6| ounces 

 of water, and from the lungs 20^ ounces, making together 27^ 

 ounces. Now is it not clear that this important process in 

 the animal oeconomy must be variously affected by the hygro- 

 metrical state of the atmosphere ; differently when the dew- 

 point is at 50° to what it will be when at 60°, 70°, 80°, or 90°? 

 Were the dew-point to be carried up to 98°, this process, it 

 would appear, must stop, evaporation would cease, and the 

 27^ ounces of water would remain in the system, or be dis- 

 posed of by nature in some different mode, which would 

 constitute a material derangement of the animal oeconomy. 

 Again, it requires a considerable portion of caloric to va- 

 porise 27| ounces of water ; and when this quantity of water 

 is daily thrown off' by evaporation, it is presumed that the re- 

 quisite quantity of caloric is abstracted from the human body. 

 Evaporation seems indeed to be the agent that nature em- 

 ploys to regulate the temperature of the body, and when it is 

 stopped or materially impeded fever generally ensues, the tem- 

 perature of the body rises, and from 98° goes up at last to fever 

 lieator 112°. Lavoisier and Seguin estimated the average 

 loss by perspiration from the skin and lungs in twenty-four 

 hours at 2 pounds 13 ounces, of which 1 pound 14 ounces 

 were dissipated by the skin, and 15 ounces by the lungs. 

 {Iraitc Elcine7itaire de Chiinie, 3™*^ edition, 228.) The de- 

 gree of dryness of the atmosphere may, it is obvious, in- 

 fluence the whole quantity evaporated, and also the pro- 

 portions given off respectively by the external skin and 

 lungs. 



Malaria seems not to prevail in a virulent state where the 

 dew-point is below 60°. In Lincolnshire and parts of Hol- 

 land and of France the dew-point is probably sometimes 

 above that height towards the end of the summer : in those 

 countries malaria fever prevails in its mildest form, but al- 

 ways at those periods when the dew-point is presumed to be 

 the highest. In the maremma of Tuscany, the Campagna of 

 Rome, and other parts of the south-west coast of Italy, in the 

 latter part of the summer the dew-point must be high, and 

 precisely at this period of the year in these places malaria 

 prevails, and in the worst form in the hottest and dampest 

 parts. In the West Indies, in Bengal, and in the African 

 valleys the same facts are observable ; malaria is always viru- 



