490 



DISEASES OF THE SKIN. 



is wanting. A classification based upon the pathological anatomy 

 could not be accepted, because the same alteration may be found in 

 diseases of a different nature, and because the same dermatosis often 

 shows the most diverse anatomical modifications in the course of 

 its evolution. Thus, the expression papulous rash could not mean 

 a clinical entity : papules may appear in the course of a certain 

 number of skin diseases; on the other hand, several of these 

 (eczema, for instance) evolve with a whole graduating series of 

 anatomical alterations (hyperemia, pimples, vesicles, pustules, scabs, 

 and crusts). We do not see the fitness of classifying skin diseases 

 in acute and chronic forms ; there are some (eczema) which pass 

 rapidly from an acute to a chronic state, or which take both types 

 alternately. The division of dermatoses into idiopathic and 

 symptomatic is not any more warranted; urticaria, for example^ 

 which constitutes a cutaneous disease par excellence from a clinical 

 point of view, may be due to external causes (insects), or internal 

 (urticaria ah ingestis), or they may depend on another affection 

 (strangles, etc.). It is the etiology that has offered the most solid 

 basis upon which to establish a classification ; such a grouping, 

 however, would be imperfect, for the etiology of a large number 

 of dermatoses is still unknown. The division of these processes 

 into parasitic and non-parasitic must be considered as the most 

 rational, notwithstanding that the field of action of vegetable 

 parasites is not yet distinctly defined. Opinions given at the 

 present time on the pathogenic rôle of some fungi found in the 

 altered epidermis are nothing less than concordant. It is certain, 

 however, that we frequently find the integument invaded by a non- 

 parasitic dermatosis ; again, it may be covered by vegetable micro- 

 organisms which are absolutely harmless. 



In cutaneous diseases produced by parasites we will establish two 

 categories : animal 'parasitic diseases and vegetable parasitic diseases. 

 Certain eruptions which are due to internal causes (variola, aphthous 

 fever, etc.), and which may be designated under the denomination 

 exanthematous, will be described in the article on Contagious 

 Diseases. We shall not deal with the numerous cutaneous altera- 

 tions (erysipelas, phlegmon, panaris, skin neoformations, etc.) which 

 belong to the domain of surgery. 



[The various expressions used to denominate the primary and 

 secondary morbid phenomena of cutaneous diseases have a special 

 significance and should not be used indifferently. 



