ECZEMA. 753 



Causation. — In end^eavouring to appreciate those agencies 

 and influences which operate in the production of catarrhal 

 inflammation of the skin, it will be found that these Lear a not 

 very distant relationship, as to modes of action manifested, to 

 such adverse influences as tend to the development of a similar 

 inflammatory action in internal mucous membranes. Regard- 

 ing eczema in its various manifestations as essentially a disturb- 

 ance in the nutritive activities of the skin, we observe that 

 this disturbance may, in a general Avay, be accepted as the 

 result of causes operating from without or from within the 

 animal itself There is amongst dermatologists much difler- 

 ence of opinion as to the relation which subsists between the 

 vascular disturbance in eczema and the observed activity in 

 cell-proliferation, whether the latter ought to be looked at in 

 the light of cause or effect, or if both ought not rather to be 

 regarded as dependent on nerve paresis. 



Of extrinsic influences we are aware that several chemical 

 or mechanical agents may develop irritation sufflcient to be 

 represented by the assemblage of phenomena recognised as 

 eczema ; while of influences operating from within, indigestion 

 and perversion of some of the various activities connected with 

 food assimilation seem to bear no unimportant part. In 

 secondary digestion we may also have the operation of such 

 disturbing influences as retention in the blood of excremen- 

 titious materials, which, circulating in the capillaries of the 

 skin, may not inaptly be regarded as active local irritating 

 agents. In all probability everything, whether of a systemic 

 and general character or merely local influence, which interferes 

 with or disturbs in any way the healthy nutrition of the skin 

 is to be regarded as a source of eczema. In those instances 

 where we may be able to appreciate and recognise with tolerable 

 certainty the agencies operating in these perversions of nutritive 

 activity, it will usually be observed that they are in particular 

 of the character which we may designate local, and the 

 phenomena or symptoms of the disturbance are local also. 

 When the causes seem to proceed from general or constitutional 

 improprieties, or the existence of loaded or contaminated blood, 

 the eczema is more frequently general than local in its develop- 

 ment. As respects the particular local changes, the proliferation 

 and intimate character of the developed cell-elements in the 



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