GENERAL PATHOLOGY. 15 



(3.) Changes in the Inflamed Tissues. — Inflammation leads 

 to depression of vitality, degeneration and death of the tissues 

 involved. No increased vitality and no multiplication of 

 tissue elements, form part in the process. 



The essential lesion of inflammation is some change in 

 the vessel-walls themselves. That these are aff'ected is shown 

 by the facts that all the early phenomena of inflammation 

 are vascular, that injury of the vessels alone causes inflam- 

 mation, and that injury of the tissues alone (Senftleben) 

 does not cause them. 



Furthermore, Eyneck has shown that stasis may be pro- 

 duced in the vessels of the web of the foot of the frog, in 

 which milk or defibrinated blood is circulating in place of 

 normal blood ; and that no such stasis can be produced in 

 vessels whose vitality has been destroyed by the injection of 

 metallic poisons. 



In all spontaneous inflammations the cause is first probably 

 carried to the part by the blood, and acts firstly upon the 

 vessels, and afterwards upon the tissues. There is no de- 

 tectable structural alteration of the vessels, and so Cohn- 

 heim speaks of the change as molecular, and regards it as 

 possibly chemical in nature. 



Clinical Signs of Inflammation, and their Causes. — The 

 clinical signs of inflammation are redness, heat, swelling, pain, 

 and impaired function. 



Kedness and heat depend upon the amount of blood pass- 

 ing through the part in a given time. Heat is not p'oducecl 

 in excess in the inflamed tissues. 



Swelling arises from exudation of fluid and cells. It 

 may be entirely due to fluid, as in hydrocele, or to 

 cells mainly, as in orchitis, w^here the fluid has been ab- 

 sorbed. 



Pain is due to pressure of the efl'usion on the nerve-end- 

 ings, and perhaps also to chemical irritation of them. The 



