192 ANATOMY AND PHYSIOLOGY. 



strained off in a liquid state from the blood-vessels, as the exhala- 

 tion is less, and' vice versa. The cutaneous and urinary excre- 

 tions seem to be vicarious, not merely in regard to the amount of 

 fluid which they carry off from the blood, but also in respect to 

 the solid matter which they eliminate from it. It appears that at 

 least one hundred grains of eifete azotized matter are daily thrown 

 off from the skin; and any cause which checks this excretion, must 

 increase the labor of the kidneys, or produce an accumulation of 

 noxious matter in the blood. Hence attention to the functions 

 of the skin, at all times a matter of great importance, is peculiarly 

 required in the treatment of febrile diseases ; and it will be often 

 found that no means is so useful in removing the lithic acid deposit 

 in diseases of the kidneys, as copious alkaline ablution and friction 

 of the skin, combined with exercise. The exhalant action of the 

 skin is completely checked by the application of an impermeable 

 varnish, the effect is not (as might be anticipated) an elevation of 

 the temperature of the body. A partial suppression by which 

 means gives rise to febrile symptoms, and there is an escape of the 

 albuminous part of the blood into the urinary tubes, in consequence 

 (it would appear) of the increased determination which then takes 

 place towards the kidneys. These facts are interesting, as throw- 

 ing light upon the febrile disturbance which accompanies those 

 febrile and cutaneous diseases that affect the whole surface of the 

 skin at once, and interfere with its functions ; and as accounting 

 also for the albumen which frequently manifests itself during their 

 progress, especially in fever. 



The exhaling powers of both the skin and the lungs are very 

 considerable. In winter, we notice the watery vapor coming from 

 the lungs condensed by the cold air ; in summer, we see how much 

 fluid escapes from the skin in the form of perspiration. Inde- 

 pendently of this, however, from thirty to sixty ounces of watery 

 fluid are calculated to pass off daily from the skin in the form of 

 insensible perspiration. This insensible perspiration may be seen 

 to be condensed, when the point of the finger is moved along the 

 surface of a looking-glass, at about the distance of an eighth of an 

 inch, and also when we handle any polished steel instrument ; or 

 still more decisively when the arm is confined in a glass jar ; or 

 when the body is viewed by a microscope in a state of free perspira- 

 tion. It is then seen enveloped in a cloud or vapor ; this comes in 

 contact with the cold of the atmosphere, which condenses it, when 

 it falls down in the form of water or sweat, being then heavier than 



