11 
which renders it necessary far us to state the sense 
in which we employ that term. In every science, 
precision in the use of terms is essential to correct 
reasoning; but in physiology, which embraces the 
properties and habitudes both of living and inanimate 
bodies, this condition is more indispensably requi- 
red ; and the uniform observation of it demands 
scarcely less attention than the process of reasoning 
itself. Add to this, that physiology, besides possess* 
ing a language of its own, converses extensively 
with almost every branch of science, and is there- 
fore perpetually exposed to the danger of ambiguity, 
from the transference and misapplication of terms. 
Hence it has happened that its doctrines and its lan- 
guage have inclined sometimes to mechanical, at 
other times to chemical, science, and, not unfre- 
quently, they have assumed a metaphysical aspect. 
215. But whatever meaning the mechanical or 
chemical philosopher may attach to the word absorp- 
tion^ the physiologist can, with consistency, employ 
it to express only that operation by which fluids are 
received into the body through a living organized 
structure, or system of vessels. Such an operation 
differs from the imbibition of fluids by inanimate bo- 
dies, which is sometimes named absorption : it dif- 
fers also from the attraction of gaseous bodies by 
fluids or by solids, which often passes under the same 
name : and, finally, it differs from the ascent of 
fluids in capillary tubes, which, whatever be its cause, 
does not partake of the nature of a living action. 
In all our investigations, therefore, we have constant- 
ly used the word absorption in its proper physiologi- 
