182 DR ALISON’S OBSERVATIONS ON 
principle as established, it goes far to explain several facts, long regarded as 
obscure, in regard to the structure and position of the lymphatic and lacteal ves- 
sels. We know that the mode of origin of these vessels gives time and opportu- 
nity for cellular action, (2. e, the development, growth, and rupture of cells,) 
and consequent chemical changes, at their extremities; we know that such 
cellular action does in fact go on there, particularly in the lacteals; and we know 
that the substances absorbed there, and probably elsewhere, by these vessels, are 
in fact altered, and so far assimilated, in the act of absorption ; as in the case, 
already mentioned, of bile absorbed from the intestines. Thus we are led to see 
the importance of these vessels being placed at all points where substances are to 
be absorbed, which are foreign to the animal economy, or require chemical change, 
in order that they may be introduced with safety or good effect. Hence, also, 
we see the use of the lymphatic glands, at which another opportunity for cellular 
action, for chemical changes and assimilation, according to the observations of 
Mr Goopsir, is provided.* And this also enables us to understand a general fact, 
which, although disputed, I believe to be both true and important in pathology,— 
that a substance destined for excretion, but retained in the blood by reason of 
disease of its excreting gland (particularly the bile or urine), is more injurious 
than the same matter when secreted by the gland, but re-absorbed from a mucous 
surface, and consequently subjected to cellular action, and thereby to chemical 
change. 
Ii. Another general fact appears to be sufficiently illustrated by observa- 
tions on the chemical changes in living bodies,—viz., That the vital properties by 
which these are effected are transferred from the portions of matter already pos- 
sessing them, to those other portions of matter which are either taken into their 
substance, or deposited in their immediate neighbourhood. It is, indeed, obvious, 
that if we are right in saying that living matter possesses these peculiar vital 
properties, the act of assimilation which we know to be continually going on in 
living bodies, is not merely the attraction and addition of new matter, but must 
include this transference of vital properties to the matter which is continually 
added to the existing solids. 
“‘ The force with which life is kept up,” says Professor WHEWELL, “ not only 
produces motion and chemical change, but also vitalizes the matter on which it 
acts, giving it the power of producing the same changes in other matter, and so on 
indefinitely. It not only circulates the particles of matter, but puts them in a 
stream, of which the flow is development as well as movement.”—(Philosophy of 
Inductive Sciences, vol. ii., p. 52.) 
Several facts which are known in physiology and pathology, may be noticed 
as more special exemplifications of this principle. Thus, we know that vessels in 
* See Carpenter’s Manual of Physiology, § 493. 

