178 DR ALISON'S OBSERVATIONS ON 



ence of the action of which, at these points, is determined by no other condition, 

 that we can see, than then- jjosition. 



This mode of limitation of the vital affinities by which the selection and ap- 

 propriation of living matter is effected, is only a statement of fact, and the most 

 general fiict that has been ascertained; and it seems highly probable, that it will be 

 found an ultimate fact, in this department of science. It may serve to familiarize 

 our minds with this principle to observe, Jirst, that it is precisely analogous to 

 the principle which is now well established as a first truth in the physiology of 

 the nervous system, that portions of nervous matter, precisely similar in structure 

 and composition, have perfectly different endowments according to the anato- 

 mical position which they occupy ; and, secondhj, that the same principle seems 

 distinctly exemplified in various cases of diseased action. The phenomena of 

 inflammation, and especially the easy recurrence of inflammation once excited 

 at any one spot in a living animal, indicate that certain vital attractions and 

 affinities existing among the particles of the blood, and between them and the 

 surrounding textures, are peculiarly modified, not merely in a paiiicular manner, 

 but exclusively at a particular spot. From the spot where it commences {e. g., 

 on a serous membrane), this alteration of vital actions extends, as from a centre, 

 to parts that are contiguous to, although having no vascular connection with, 

 that where it commenced, as we see in tracing it from one fold of the peritoneum 

 to another. And when we examine the results of the inflammation in the dead 

 body, we see what clearly shews the operation of a force, producing chemical 

 changes of the kind we are now considering, but acting only at one part, and 

 in one direction. " The capillaries which have taken on the appearance of inflam- 

 mation, are all on one side of the fine membrane, and the serum and lymph, effu- 

 sions fi'om these vessels," by which the diseased state is essentially characterized, 

 " are all on the other." — (Goodsik, Anatomical and Pathological Observations, p. 43.) 



In saying that the fundamental property of chemical selection, essential to 

 the growth of all hving bodies, is strictly a vital property, we do not overlook the 

 fact that various substances, composed of inanimate or inorganic matter, have 

 likewise different powers of attraction for different elements or compounds 

 brought into contact with them. It appears to be only by reference to this pro- 

 perty, that we can explain the well-known phenomena of endosmose and ex- 

 osmose, in which different fluids, brought in contact with a solid body, are 

 attracted into its pores with very different degrees of force. It is not the nature 

 of the process by which the selection, in the case of the living body, is effected ; 

 but the peculiarities of the selections themselves, their great force, and yet uniformly 

 temporary existence, that entitle us to regard them as indicating a vital property. 



II. But when we attend to the peculiar changes effected by living solids on 

 the fluid matters which are brought in contact with them, we find that these are 

 by no means confined to the selection and appropriation, at particular points, of 



