PRINCIPLES OF VETERINARY SURGERY 41 



sues must have the power to combine with toxin before the 

 inflammation can be produced. Many animals possess a 

 marked resistance to bacterial invasion. This must be low- 

 ered before infection can take place. Second, virulence of 

 bacteria. Bacteria cannot produce disease unless they are in 

 a very active and virulent condition, and usually a large 

 number of them gain entrance to the body at the same time. 

 Third, a previous or concurrent injury. The tetanus bacilli 

 are usually carried in with a nail, the staphylococci enter 

 through some abrasion, etc. As soon as there is an abrasion 

 of the skin or injury of some tissue, the way is opened for 

 bacteria to enter the body and set up an inflammatory pro- 

 cess. 



Inflammations due to traumatic, thermal and chemical 

 injuries are completely dealt wiith in chapter on Traumatism. 



CLASSIFICATION.— The classifications of inflamma- 

 tion are various. In general we may classify them as acute 

 and chronic. The acute form is rapid in onset, of short dura- 

 tion, and has a tendency to produce pus in the tissue. Strep- 

 tococcus, staphylococcus and bacillus pyocyaneus enter 

 largely into this form. Chronic inflammation is insidious in 

 onset, protracted in duration, and characterized by progres- 

 sive lesions in the tissue; it shows little tendency to recover. 

 Fistulse and ulcers are examples of chronic inflammations. 

 They heal with the formation of cicatricial tissue, or a scar. 



Inflammations may be further classified according to 

 their location in the tissue, and the kind of irritation pro- 

 duced during the reaction: 



1. Parenchymatous, involving largely the essential func- 

 tionating cells of an organ, as in anthrax. 



2. Interstitial, affecting the supporting connective-tis- 

 sue frame work, or stroma, of an organ; found in chronic 

 conditions. 



3. Catarrhal, affecting the mucous membranes with a 



