296 ABSORPTION. 



being, like the membranous septum of the eudosmometer, por- 

 ous and capable of imbibing fluids, and of the blood being so 

 composed that most fluids will mingle with it. The process of 

 absorption, in an instructive, though very imperfect degree, 

 may be observed in any portion of vascular tissue removed 

 from the body. If such a one be placed in a vessel of water, 

 it will shortly swell, and become heavier and moister, through 

 the quantity of water imbibed or soaked into it; and if now, 

 the blood contained in any of its vessels be let out, it will be 

 found diluted with water, which has been absorbed by the 

 bloodvessels and mingled with the blood. The water round 

 the piece of tissue also will become bloodstained ; and if all 

 be kept at perfect rest, the stain derived from the solution of 

 the coloring matter of the blood (together with which chemistry 

 would detect some of the albumen and other parts of the liquor 

 sanguinis) will spread more widely every day. The same will 

 happen if the piece of tissue be placed in a saline solution in- 

 stead of water, or in a solution of coloring or odorous matter, 

 either of which will give their tinge or smell to the blood, and 

 receive, in exchange, the color of the blood. 



Even so simple an experiment will illustrate the absorption 

 by bloodvessels during life ; the process it shows is imitated, 

 but with these differences : that, during life, as soon as water 

 or any other substance is admitted into the blood, it is carried 

 from the place at which it was absorbed into the general cur- 

 rent of the circulation, and that the coloring matter of the 

 blood is not dissolved so as to ooze out of the bloodvessels into 

 the fluid which they are absorbing. 



The absorption of gases by the blood may be thus simply 

 imitated. If venous blood be suspended in a moist bladder in 

 the air, its surface will be reddened by the contact of oxygen, 

 which is first dissolved in the fluid that moistens the bladder, 

 and is then carried in the fluid to the surface of the blood : 

 while, on the other hand, watery vapor and carbonic acid will 

 pass through the membrane, and be exhaled into the air. 



In all these cases alike there is a mutual interchange be- 

 tween the substances ; while the blood is receiving water, it is 

 giving out its coloring matter and other constituents : or, while 

 it is receiving oxygen, it is giving out carbonic acid and water; 

 so that, at the end of the experiment, the two substances em- 

 ployed in it are mixed ; and if, instead of a piece of tissue, one 

 had taken a single bloodvessel full of blood and placed it in 

 the water, both blood and water would, after a time, have been 

 found both inside and outside the vessel. In such a case, more- 

 over, if one were to determine accurately the quantity of water 

 that passed to the blood, and of blood -that passed to the water, 



