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The immediate cause or causes of this disorder may (in 

 common with other blood diseases) depend upon a chemical 

 and dynamic change in the blood. We have endeavored to 

 show how this occurs in a former article, and it may be 

 repeated here. It originates at least in two ways : First, by 

 the non-excretion (and consequent accumulation in the 

 blood) of excrementitious substances which, by their own 

 properties, or by the chemical changes they undergo, prove 

 highly injurious to the system ; or, secondly, by the mtro- 

 duction into the blood of morbid substances from without. 



The effects of these poisons when introduced or retained 

 in the bodies of animals are both local and constitutional. 

 The constitutional symptoms, which always begin the attack, 

 are nearly alike for them all : but the local symptoms are 

 peculiar to each. There is one fact in connection with this 

 subject worth remembering, and that is, that the poison 

 resulting from the non-elimination of the excretions is never 

 a primary and independent affection. It therefore must be 

 studied in connection with those disorders of which it forms 

 a secondary or resultant, though important part. A right 

 understanding of these facts will enable us at once to under- 

 stand the nature and symptoms of purpura h?emorrhagica: 



Symptoms. — We have endeavored to show that when 

 such diseases as influenza, pneumonia, or strangles are 

 neglected or mismanaged, or when these diseases are pro- 

 longed, there is engendered and retained in the system some 

 specific poison which reduces the vitality of the blood ; this 

 is seen in the diminished quantity and altered condition of 

 the fibrine of the blood, which renders it thin and imperfectly 

 coagulable. 



When the blood is thus thin and impoverished it is imper- 

 fectly retained in the badly nourished vessels, and becomes 

 extravasated on the mucous surfaces. When the disease has 

 progressed this far the symptoms are soon manifest to the 

 senses. This eftusion of blood may be seen in spots in the 

 nostrils, within the lips, and about the head ; from these red 



