1304 PHYSIOLOGY 



The action of pilocarpine, as well as the effects of artificial stimulation 

 of the sweat-nerves, is abolished by the administration of atropine. 



THE GASEOUS EXCHANGES OF THE SKIN. In any animal 

 with a thin moist skin, such as the frog, the absorption of oxygen and 

 the excretion of C0 2 from the skin may be sufficient for the proper 

 aeration of its blood, so that it may continue to live after the 

 extirpation of its lungs. In man there is also a continuous output 

 of C0 2 through the skin, but the amount leaving the body in this 

 .way is negligible compared with that which is exhaled through the 

 lungs. The loss of C0 2 by the skin rises with increase of external 

 temperature. Thus at a temperature of 29 to 33 C. the C0 2 output 

 by the skin is about 0-35 grm. per hour, i.e. about 84 grm. in the 

 twenty-four hours. When the external temperature rises above 

 33 C., the C0 2 output increases, so that at 34 it is doubled and at 

 38-5 it may amount to as much as 1-2 grm. per hour (Schierbeck). 

 It is just at this temperature of 33 C. that a secretion of sweat 

 begins to be noticeable, so it has been suggested that the increased 

 C0 2 output may be due directly to the increased work and metabolism 

 of the sweat-glands during their activity. 



ABSORPTION BY THE SKIN. In order to test the alleged 

 influence of baths containing medicinal substances in solution, many 

 experiments have been made to determine whether absorption is possible 

 by the skin. It may be regarded as established that the uninjured 

 skin is impermeable for watery solutions of salts or other substances. 

 On the other hand, it is possible to produce a certain amount of 

 absorption by the inunction of substances dissolved in fatty vehicles. 

 Thus the administration of mercury is often carried out by the 

 inunction of mercurial ointments, and the fact that mercurial salivation 

 may be produced in these conditions shows that a certain amount of 

 the mercury must have been absorbed. It is difficult to imagine that 

 any appreciable amount of cod liver oil will be available for the 

 nutrition of the infant when this substance is administered by rubbing 

 it on the skin. On the other hand, the moist mucous surfaces, such as 

 the conjunctiva or the mucous membrane of the respiratory passages, 

 as well as raw surfaces of the skin, e.g. which have been deprived of their 

 epidermal layer by the application of blisters, permit of the rapid 

 passage of substances in watery or oily solution. 



