RAPIDITY OF ABSORPTIOX. 371 



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 vapour 

 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 colouring 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 employed in it are mixed ; and if, instead 

 of a piece of tissue, one had taken a single blood-vessel 

 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, moreover, if one were 

 to determine accurately the quantity of water that passed 

 to the blood, and of blood that 'passed to the water, it 

 would be fouri that the former was always greater than 

 the latter. And so with other substances; it almost always 

 happens, that if the two liquids 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. 



The rapidity with which matters may be absorbed from 

 the stomach probably by the blood-vessels chiefly, and dif- 

 fused through the textures of the body, may be gathered 

 from the history of some experiments by Dr. Bence Jones. 

 From these it appears that even in a quarter of an hour 

 after being given on an empty stomach, chloride of lithium 

 may be diffused into all the vascular textures of the body, 

 and into some of the non-vascular, as the cartilage of the 

 hip-joint, as well as into the aqueous humour of the eye. 

 Into the outer part of the crystalline lens it may pass after 

 a time, varying from half an hour to an hour and a half. 



B B 2 



