164 PHYSIOLOGY. 



set up osmotic pressure, tending to make the blood and lymph 

 similar in composition. 



The formation of lymph in the tissues takes place continually 

 and without interruption. The amount of lymph increases with the 

 activity of the organ from which it proceeds, while active or even 

 passive movements of the muscles greatly increase its amount. 



It may be roughly stated that the amount of lymph and chyle 

 combined passing through the large vessels in twenty-four hours is 

 about 2 pounds. 



Skin and Lungs. 



It remains to consider the nature of the absorption that takes 

 place through the skin and lungs. These avenues are but subsidiary 

 ones to the two greater ones just mentioned: intestinal absorption 

 and that along the lymphatic system. Absorption through them 

 takes place from without; so that it is usually classed with the first 

 of the two processes of absorption mentioned at the beginning of 

 this chapter. 



For a long time it was a subject for much discussion whether 

 water was absorbed by the skin with the epidermis still intact. It 

 was a rather difficult matter to ascertain, since the skin is constantly 

 giving off water in the form of perspiration, sensible or insensible. 

 The absorption of water through the skin covering the body takes 

 place very rapidly in the lower animals. It has been finally ascer- 

 tained that absorption of water does take place through the skin of 

 man, but to a much less degree than in animals. Aqueous solutions 

 of various drugs when in simple contact with the skin are only 

 slightly active. It is believed that the great hindrance to their 

 absorption is the presence of the fat that is normally present upon 

 the skin and in its pores and interstices. If this be removed by the 

 application of alcohol, ether, or chloroform, physiological effects of 

 the drugs are soon manifested. 



Inunction. When ointments are rubbed into the skin absorp- 

 tion will take place. Mercury, when applied in this manner, exerts 

 its specific effect upon syphilis and excites salivation; tartar emetic 

 so applied may produce vomiting or an eruption extending over the 

 entire body. Voit found globules of mercury between the layers of 

 the epidermis and even in the corium of a person who had been 

 executed and into whose skin mercurial ointment had previously 

 been rubbed. An abraded or inflamed surface absorbs very rapidly. 



Under normal conditions minute traces of are absorbed from 



