254 ON THE CHANGES OCCURRING IN 



in the shape of spicula, rods, &c. Nitric acid being 

 then added, these particles were dissolved. On 

 heating a portion in the flame of a lamp, a copious 

 white ash was left, which was not dissolved by acetic 

 acid, but disappeared in nitric acid with very slight 

 effervescence. 



Such being some of the more frequent changes 

 which impaired vitality produces in the internal 

 organs of the body, it becomes a point of considerable 

 interest, and great practical importance, to determine, 

 as far as possible, the conditions which regulate the 

 production of each of these particular effects. For 

 by acting upon those conditions, we may sometimes 

 hope to beneficially influence, or give a particular 

 direction to, the change, or series of changes, oc- 

 curring in different cases. 



The investigation of this part of the subject has 

 scarcely yet been commenced, but there are certain 

 conditions which evidently affect the production of 

 these pathological changes, among which may be 

 enumerated the following : - 



1. The chemical composition and physical struc- 

 ture of the tissues of the affected part, the relative 

 proportion of liquid and solid matters which they 

 contain, &c. 



2. The physical and vital condition of the adjacent 

 structures, their relative absorbing power, &c. I 

 may illustrate this law by reference to the very 

 different results which I obtained in experiments 

 wherein the condition of the adjacent parts was the 

 only essential variation. In the experiment already 

 related at length, it was seen that the complete ob- 



