infijuimatiox. 163 



animal. The blood is bright red in the arteries, and is 

 known as ' arterial blood.' It is of a dark red in the veins, 

 and is known as 'venous blood.' It is perfectly natural 

 lor healthy blood to coagulate and separate into two parts. 

 On placing blood in a bottle or other vessel this change 

 will take place in from fifteen minutes to half an hour. The 

 solid portion is composed of corpuscles and fibrin, while the 

 serum is formed of albumen and the various salts. The 

 addition of soda to freshly-drawn blood will prevent coagu- 

 lation to a certain extent ; while chlorate of potassium will 

 cause it to coagulate and remain in that condition. 



INFLAMMATION. 



Definition.^^An alteration in the healthy structure and 

 functions of the affected part, accompanied by a perverted 

 condition of the blood in the capillaries, all of which may 

 be considered as due to a certain amount of paralysis in the 

 vital principle of the tissues inflamed {Smith). 



The phenomena of inflammation have excited inquiry, 

 and been subjects of controversy amongst votaries of the 

 medical science for ages. Half a century ago inflammation 

 was considered to be caused by increased nutrition and 

 determination of blood to the part aff'ected. Another 

 definition of inflammation is, 'an exudation of lymph or 

 liquor sanguinis.' Before inflammation takes place there 

 occurs a change called hyper^emia, or congestion. "When the 

 blood exists in too great abundance in one particular grgan 

 or tissue, without any particular change taking place, it is 

 known as healthy or active congestion, caused by active 

 work or exertion. Again, it may be caused by nervous in- 

 fluence, in illustration of which may be mentioned a blush, 

 or anger causing the cheeks to flush or become pale. It 

 either decreases insensibly, or may in some cases give rise 

 to haemorrhage, etc. When the flow of blood to the heart 



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