INFLAMMATION". 



[ 412 ] 



INFLAMMATION. 



inflammation are best studied in one of the 

 lower animals, as in the web of the frog's 

 foot, the mesentery of the frog, the tail of 

 the tadpole, or of the larva of the water- 

 newt {Triton), the process being excited by 

 the application of a hot needle, a solution 

 of common salt, ammonia, dilute spirit, or 

 volatile oil. 



The principal phenomena are as fol- 

 lows : — 



1. Changes in the blood-vessels and circu- 

 lation. 



2. Exttdation of liquor sanguinis and mi- 

 gration of white blood-corjmscles ; and 



3. Alterations in the nutrition of the in- 

 earned tissue. 



1. The first eilect of irritation of the 

 mesentery (mere exposure to the air being 

 sufficient for the purpose) is to cause dila- 

 tation of the arteries, and subsequently tliat 

 of the veins. The dilatation of the arteries 

 commences at once, and is not preceded by 

 contraction. It gradually increases for 

 about twelve hours, and is associated at the 

 commencement of the process with an ac- 

 celeration in the flow of blood ; this, how- 

 ever, is soon followed by a considerable 

 retardation. These alterations in the rapi- 

 dity of the blood-flow, however, cannot be 

 owing to the increase in the calibre of the 

 vessels, which remain throughout dilated. 



The retardation of the circulation usually 

 commences somewhat suddenly, and is first 

 observable in the veins. The rapidity of 

 the current varies, however, in different 

 vessels ; in some (both arteries and veins) 

 it may be more rapid, in others very slow, 

 and either oscillating to and fro, or even 

 completely stagnant. These differences may 

 occur in contiguous vessels. The capillaries 

 and small arteries often present at the same 

 time numerous irregular bulgings and con- 

 tractions. 



As the circulation becomes slower, the 

 white blood-corpuscles (leucocytes) accu- 

 mulate in the veins. Their natural ten- 

 dency to adhere to the sides of the vessels 

 is increased, so that they may nearly fill the 

 tube. At the same time they exhibit active 

 movements, by means of which they pene- 

 trate the walls of the vessels and pass into 

 the surroimding tissues. The absolute 

 number of white blood-corpuscles may also 

 be increased o^^^ng to the irritation of the 

 lymphatic structures in the vicinity of the 

 inflamed tissue. 



The red corpuscles also accumulate in the 

 capillaries. They adhere to one another 



and to the sides of the vessels, and become 

 so closely packed that their outlines can 

 scarcely be distinguished. Increased ad- 

 hesiveness of the red corpuscles has long 

 been regarded as characteristic of inflam- 

 matory blood, by virtue of which they 

 exhibit a greater tendency to cohere in rolls 

 than in health. 



The diminution in the rapidity of the 

 circulation, and the accumulation of the 

 blood-corpuscles in the vessels, is followed 

 by the complete stagnation of the current, 

 constituting the condition long known as 

 injlam matory stasis. 



2. Another constituent of the inflamma- 

 tory process consists in the exudation of 

 liquor sanguinis and the migration of the 

 colourless blood-corpuscles. 



The migration of the colourless blood- 

 corpuscles (leucocytes) through the walls of 

 the blood-vessels was first described by 

 Addison in 1842. This observer stated that 

 in inflammation, these corpuscles adhered 

 to the walls of the vessels and passed 

 through them into the surrounding tissues. 

 In 184G Waller more fully described the 

 same phenomenon. Both these observers 

 concluded that the escaped corpuscles 

 became pus-corpuscles. Cohnheim in 1867 

 brought the subject forward ; and to him 

 we owe most of our present knowledge 

 respecting it. 



The migration may be observed in the 

 mesentery of a frog which has been pre- 

 viously paralyzed by the subcutaneous in- 

 jection of cm-are. 



The colourless blood-corpuscles which 

 accumulate in large numbers, especially in 

 the veins, remain almost stationary against 

 the walls of the vessel, the blood-current 

 passing by them, although with much 

 diminished velocity. Those immediately 

 adjacent to the wall gradually sink into it, 

 and pass through it, between the epithelial 

 cells, into the surrounding tissue. In doiug 

 so they may be observed in the various 

 stages of their passage. At first small 

 button-shaped elevations are seen springing 

 from the outer wall of the vessel. These 

 gradually increase until they assume the 

 form of pear-shaped bodies, which still 

 adhere by their small ends to the vascular 

 wall. Ultimately the small pedicle of pro- 

 toplasm bv which they are attached gives 

 way and the passage is complete, the cor- 

 puscle remaining free outside the vessel. 



The corpuscles having escaped from the 

 vessels into the surrounding tissues, coutiuue 



