354 OF NUTRITION. 



of causes, which, when less potent, occasion Inflammation, in the case 

 of frost-bites produced by Cold ; for this agent at the same time pro- 

 duces contraction of the blood-vessels, and depression of the vital 

 powers of the solid tissues, proceeding to the complete destruction of 

 them; whilst in the parts adjoining those which are actually killed, the 

 inflammatory state is developed, an effusion of fibrine being produced, 

 which serves to plug up the mouths of the vessels, and thus to prevent 

 hemorrhage, when the mortified part drops off. Here we see, that the 

 violent action of cold completely destroys the vitality of the part most 

 exposed to it; and this by its direct influence on the properties of the 

 organized structure. No inflammation can take place in the part thus 

 killed, because the vital processes are altogether brought to an end. 

 But inflammation takes place in the adjoining parts, which are less 

 seriously affected ; for the depression of their vital powers occasions 

 the result already adverted to, namely, the production of an increased 

 amount of fibrine in the blood, and an infiltration of this substance 

 into their tissues. The same is the case, with regard to the operation 

 of other powerful agents ; such as those which (like Caustic Potass, or 

 Sulphuric Acid) destroy the vitality of the parts to which they are 

 applied, by the chemical decomposition of their tissues. The Inflam- 

 matory process is set up, not in the parts which are killed by the appli- 

 cation, but in the surrounding tissues, whose vitality has been simply 

 depressed ; and thus, when the slough, or dead part, is cast off, there is 

 a preparation for the development of new tissue to supply its place, 

 from the superabundant plastic materials of the surrounding parts. 



635. If, then, we limit the term Inflammation, as there seems reason 

 to do, to that state, in which there is a tendency to stagnated circula- 

 tion, with increased production of Fibrine, in the vessels of the part, 

 we see that Gangrene cannot be a result of that process, which is one 

 rather of reparation than of destruction. But Gangrene proceeds, 

 where we can distinctly trace its causes, from the violent operation of 

 the same agents, as those which, in a less degree, produce Inflammation. 

 And where this last process is not set up at the line of demarcation 

 between the living and the dead parts, Gangrene, like Suppuration, has 

 a tendency to spread ; the influence of the decay, which is taking place 

 in one part, having a tendency to propagate itself, to the adjoining 

 tissues ; and a constantly-extending destruction being thus produced. 



636. We have now to speak of those reparative processes, by which 

 the effects of disease or injuries are more or less perfectly recovered 

 from. The healing of a simple wound may take place by the direct 

 adhesion of its walls, when they can be drawn closely together ; but 

 more frequently it is accomplished by the intermediation of a thin 

 layer of "coagulable lymph," which may be thrown out for the purpose 

 of reparation, without the existence of inflammatory action. But the 

 reparation of wounds, in which there has been so great a loss of sub- 

 stance that neither direct nor indirect adhesion can take place, is 

 accomplished by the gradual development of new tissue from the 

 " nucleated blastema" with which the cavity is first filled. This, 

 however, may occur in two very different modes ; and from the inqui- 

 ries of Mr. Paget it appears that the determination of one or the other 



