ABSORPTION BY BLOOD-YESSELS. 375 



happens, that if the two fluids placed on opposite sides of 

 a membrane be of different densities or specific gravities, 

 a larger quantity of the less dense fluid passes into the 

 more dense, than of the latter into the former. 



While the question was being discussed, whether ab- 

 sorption (using the term generally) were effected by the 

 lymphatics or the veins, many experiments were formed 

 to demonstrate the fact of absorption by the blood-vessels, 

 which may be quoted, not only as evidence for that fact, 

 but in illustration of the difference between the absorption 

 by lymphatics and that by blood-vessels, in regard to the 

 materials they severally receive and convey into the cir- 

 culation. 



Yarious odorous and saline matters taken with the food, 

 or injected into the intestines of an animal, are soon found 

 in the blood of the vena portse, or other blood-vessels, or 

 in the urine, but are not found in the chyle ; or, if found 

 there, not till they may have passed into the lacteals from 

 their blood-vessels. This is shown by numerous experi- 

 ments, especially by those of Tiedemann and Gmelin, and 

 Panizza. The substances used in the experiments were 

 ferrocyanide of potassium, sulphate of potash, several salts 

 of lead, iron, and other metals, indigo, madder, rhubarb, 

 camphor, musk, alcohol, turpentine, etc. Mayer also, when 

 he injected ferrocyanide of potassium into the lungs, found 

 it in the left side of the heart sooner than in the right ; 

 showing that it had taken the course of the blood, not of 

 the lymph, which would have carried it to the right side 

 of the heart first. All these substances, therefore, appear 

 to be absorbed by blood-vessels exclusively. 



Again, if any of these substances be included within a 

 portion of an animal's intestine tied at both ends, and if 

 all the vessels of that portion of the intestine be cut away, 

 except its artery and vein, the substances being absorbed 

 will be found in the blood of the vein ; but, if the main 

 arteries and veins be tied, and the lacteals left entire, the 



