INFLAMMATION AND PHAGOCYTOSIS 131 



The four cardinal symptoms redness, heat, pain and swelling 

 represent only an external definition of inflammation. The 

 sum total of the facts is so complex that many observers in. 

 former days refused to give a simple definition, proposed to 

 abandon the vague term of inflammation, and limited themselves 

 to a description of the variety of facts. 



The tissues, the vessels, and the nerves of the injured part 

 participate in the state of inflammation : to which is the 

 primary role to be ascribed ? Virchow maintained that it was 

 the tissues, and that these were in a state of supernutrition at 

 the expense of "Cos. fluid parts of the blood ; the cells multiply 

 at the injured point and it is from the tissues of this same 

 region that the numerous cells of the inflammatory exudate 

 are derived. Inflammation taken as a whole represents a 

 danger to the body. 



But when Cohnheim, in his observations on the frog's 

 mesentery exposed to the air, discovered diapedesis or the 

 escape of the white corpuscles through the walls of the 

 vessels, and when it was established that the pus cells instead 

 of developing on the spot by the proliferation of the cells of 

 the connective-tissue came from the motile cells of the blood, 

 the primary fact of inflammation seemed to be the vascular 

 irritation, the other appearances being secondary. Cohnheim 

 thought he had proved this by his well-known experiment ; a 

 frog's tongue is ligatured at the base so as to stop the 

 circulation. On untying at the end of forty-eight hours the 

 circulation is re-established, but is now of the inflammatory 

 type with diapedesis. 



But if the vascular phenomena are of primary importance 

 it is difficult to account for the fact that microbial or other 

 foreign substances introduced under the skin produce an 

 inflammatory reaction, but fail to do so when injected into the 

 vessels themselves. 



Light was first thrown on the problem by the comparative 

 study of lower organisms. 



Inflammation in the Lower Organisms. — The jelly- 

 like Plasmodium of a mycetozoon pricked or burnt responds 



K 2 



