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, (i. 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 Avhich another ojiportunity for cellular 

 action, for chemical changes and assimilation, according to the observations of 

 Mr GooDSiR, 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 fi-om a mucous 

 surface, and consequently subjected to cellular action, and thereby to chemical 

 change. 



III. 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 kno^vn in physiology and pathology, may be noticed 

 as more special exemplifications of this principle. Thus, we know that vessels in 



* See CAnpENTER's Manual of Physiology, § 493. 



