INFLAMMATION. 323 



concentrated. The exciting causes of inflammation are various, 

 among which the following are included: Mechanical injury^ the 

 result of a wound or bruise; chemical irritants, as when a can- 

 tharides blister is applied to the skin; excessive heat or cold, as 

 when an animal is exposed to sudden and extreme changes of 

 temperature; and the introduction into the system of deleterious 

 animal products like bacteria. 



We have already stated that inflammation may be either general 

 or local; after we have attempted to explain the actual changes 

 that take place as the result of inflammation, or rather that are 

 dependent upon the condition known as inflammation, it will be 

 seen why it is that inflammation of the local order occurs much 

 more frequently than the general; by this we wish to be under- 

 stood as meaning that special organs, as the lungs, kidneys, liver, 

 et cetera, and very frequently only limited areas of these organs 

 are more often the seat of the changes involved in the inflam- 

 matory process than the body generally. The changes which 

 take place in the process called inflammation involves, ist. The 

 blood, the blood vessels and the circulation of the blood. 2d. 

 The tissues through which the blood vessels so affected ramify 

 and extend. 



In the first place we must remind the student what the compo- 

 sition of the blood is; and in so doing shall refer onh' to its three 

 principal constituents: (a) The liquor sanguinis or fluid portion; 

 (^b^ the red corpuscles, and (r) the white corpuscles or leucocytes. 

 The red corpuscles are circular, convex at the edges, and concave 

 at the centres; thej' form about forty per cent, of the entire mass 

 of the blood, and are the cause of its color and density. The 

 white corpuscles are far less numerous than the red, and in com- 

 parative weight much lighter, evidence of which appears when 

 blood coagulates or forms into a clot, the light colored portion al- 

 ways coming to the top; the shape of a white corpuscle varies 

 considerably; if a single drop of blood is placed upon a glass 

 slide, covered with a slip, and thereafter examined under a micro- 

 scope, the red blood cells will be easily discerned by their shape 

 and also by their movements, they keep up a continual .stream, by 

 rapidly passing from one end to another of the slide, while the 

 white corpuscles adhere to the sides of the slide. 



Whatever maj' be the cause of inflammation its consequen..es 



