60 THE SKIN A REGULATOR 0? A&IMAL 



landing. On the other hand, this function of the 

 skin is so much weakened, almost paralyzed, when 

 the climate frbm which a person is passing is dry 

 and bracing, and that into which he has passed is 

 humid and relaxing, that congestions of blood take 

 place in the larger vessels, the body becomes sus- 

 ceptible of the least impression of marshy exhala- 

 tions, and agues and similar diseases are produced.' 1 

 We shall now be able to understand why in 

 ummer we suffer most from heat in what is called 

 moist close weather, when no air is stirring ; and 

 why warm climates, which are at the same time 

 moist, are proverbially the most unwholesome. 

 The chief reason is the diminished evaporation from 

 the skin which such a condition of the atmosphere 

 produces, partially shutting up the natural outlet of 

 the superfluous heat of the body ; and as it at the 

 same time checks the exit of the waste matter 

 which ought to be thrown out, and which is known 

 to be as injurious to the system as an active poison 

 taken into the body from without, the hurtful con- 

 sequences of such weather and climates, and the 

 fevers, dysenteries, and colds to which they give 

 rise, are partly accounted for. This is one powerful 

 reason why night air is so unwholesome, particularly 

 in malaria districts, which are loaded with moisture 

 and miasma ; for, when the air is dry as well as hot, 

 and free evaporation takes place, little or no in- 

 convenience is felt, and health oftener remains un- 

 injured. Delaroche has established this point con- 

 clusively by experiment. He exposed animals to a 

 very high temperature in a dry air, and found them 

 to sustain no mischief ; but when he exposed them 

 in an atmosphere saturated with moisture, to a heat 

 only a few degrees above that of their own bodies, 

 and greatly lower than in the former instance, they 

 very soon died. Here we see the reason also why, 

 ii ague and other fevers, the suffering, restlessness,, 

 and excitement of the hot stage can never be abated 



