ABSOEPTION ET BLOOD-VESSELS. 367 



parts of the nervous centres were uninjured, instantly 

 arrested the heart's movements. The posterior or ischiatic 

 pair of lymph-hearts were found to be governed, in like 

 manner, by the portion of spinal cord corresponding to 

 the eighth vertebra. Division of the posterior spinal roots 

 did not arrest the movements ; but division of the anterior 

 roots caused them to cease at once. 



Absorption by Blood-vessels. 



The process thus named is that which has been com- 

 monly called absorption by the veins ; but the term here 

 employed seems preferable, since, though the materials 

 absorbed are commonly found in the veins, this is only 

 because they are carried into them with the circulating 

 blood, after being absorbed by all the blood-vessels (but 

 chiefly by the capillaries) with which they were placed in 

 contact. There is nothing in the mode of absorption by 

 blood-vessels, or in the structure of veins, which can make 

 the latter more active than arteries of the same size, or so 

 active as the capillaries, in the process. 



In the absorption by the lymphatics or lacteal vessels 

 just described, there appears something like the exercise 

 of choice in the materials admitted into them. But the 

 absorption by blood-vessels presents no such appearance 

 of selection of materials; rather, it appears that every 

 substance, whether gaseous, liquid, or a soluble or minutely 

 divided solid, may be absorbed by the blood-vessels, pro- 

 vided it is capable of permeating their walls, and of 

 mixing with the blood ; and that of all such substances, 

 the mode and measure of absorption are determined solely 

 by their physical or chemical properties and conditions, and 

 by those of the blood and the walls of the blood-vessels. 



The phenomena are, indeed, exactly comparable to that 

 passage of fluids through membrane, which occurs quite 

 independently of vital conditions, and the earliest and best 

 scientific investigation of which was made by Dutrochet. 



