276 Dr Alison on the Principle of Vital Affinity. 



a statement of fact, and the most general fact tliat 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, 

 firsty 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 anatomical position which they 

 occupy; and, secondly^ that the same principle seems distinctly 

 exemplified in various cases of diseased action. The pheno- 

 mena 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 particular manner, but exclusively at a particular spot. 

 From the spot where it commences [e. ^., on a serous mem- 

 brane), 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 consider- 

 ing, but acting only at one part, and in one direction. " The 

 capillaries which have taken on the appearance of inflamma- 

 tion are all on one side of the fine membrane, and the serum 

 and lymph, effusions from these vessels," by which the diseased 

 state is essentially characterized, " are all on the other." — 

 (Goodsir, Anatomical and Fathological Observations^ p. 43.) 



In saying that the fundamental property of chemical selec- 

 tion, essential to the growth of all living bodies, is strictly a 

 vital property, we do not overlook the fact that various sub- 

 stances, 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 property, that. we can explain 

 the well-known phenomena ofendosmose and exosmose, in which 



