778 CUTANEOUS HEMORRHAGES. 



able or unfavourable, of tlie general disease Avitli which they 

 are associated; and during their existence, when situated where 

 their characters may be observed, as on the membrane of the 

 nose or mouth, the colour is rarely uniform, and they may not 

 display steady and regular chromatic changes until percej)tible 

 defervescence of the fever upon which they depend is estab- 

 lished. 



Besides petechia3 and ecchymoses accompanying certain 

 general diseases and resulting from injuries mechanical and 

 parasitic, the most distinctive exhibitions of cutaneous haemor- 

 rhage seen in our patients are those associated with special 

 systemic disturbances and changes recognised under the term 

 of PuTpiira hcemorrhagica. This not being regarded as pro- 

 perly a disease of the skin, has been spoken of under another 

 class. 



In no instance may cutaneous liDomorrhage be regarded as a 

 diseased condition of itself, but rather as symptomatic of some 

 other abnormal conditions ; most probably in every instance it 

 is dependent upon some chemical alteration of the blood itself, 

 upon some disturbance of its dynamic relations, or upon some 

 textural changes occurring in the ca^jillary vessels. 



From these considerations we may understand that the suc- 

 cessful treatment of this condition depends less upon rectifica- 

 tion of local changes than upon correction of some general 

 unnatural state and the establishment of normal systemic 

 functional activity. 



Class YI. Parasitic Skin Diseases. 



Like many other structures of the animal body, the skin is 

 liable to suffer from disturbance and change, the result of the 

 association with it of distinct and separable forms of organiza- 

 tion, which derive their sustenance from it. During the growth 

 and development of these parasites certain consequences or 

 results arc exhibited which are recognised as diagnostic, as also 

 other phenomena Avhich can only be looked upon as of an 

 adventitious character. 



Cutaneous diseases originating or owing their existence to 

 parasitic life and development are usually spoken of as Derma- 

 tuzoic, or such as are dependent on animal parasites, and 



