338 MORBID ANATOMY OF THE SKIN. 



toses to the epidermis and papillary body under a common 

 law. 



§ 287. We include the large assemblage of these superficial 

 dermatoses under the name of eruptions, exanthemata. Every 

 exanthem begins with hypera?mia of the papillaiy body. This 

 is the first sign we have that the part is being irritated ; it is the 

 starting-point of all the subsequent excesses and abnonnalities in 

 its nutrition. Even at this early stage, we are struck by the 

 contrast between the manifold variety of the coarser anatomical 

 appearances, and the monotonous uniformity of the microscopical 

 alterations. The major part of general dennatology may be 

 legitimately considered as so much morbid anatomy. There is 

 nothing to hinder the anatomist from describing and distinguish- 

 ing the various naked-eye appearances, sizes, and positions of 

 the maculae, papules, bullae, pustules, &c., quite as elaborately 

 as the professed dermatologist. Pathological histology however 

 knows nothing of all this diversity ; here, as elsewhere, it shows 

 from what simple elements nature can procure the most complex 

 results. It recognises, strictly speaking, only two sets of morbid 

 changes, which, either singly or in combination, make up the 

 various exanthemata. These elementary categories may be 

 designated as the ^^simple inflammatory" and the ^^hyper- 

 trophic inflammatory," the latter serving as a convenient 

 transition to the simple hypertrophies of the papillary body, 

 such as warts, &c. These divisions coincide very fairly with 

 those based on the time which each disorder requires to run its 

 course; thus the simple inflammatory may be called rapid or 

 acute, the hypertrophic inflammatoiy slow or clu'onic, while the 

 non-inflammatory hypertrophies include those forms which seldom 

 get well if left to themselves. We must bear in mind however, 

 that the terms '' acute " and ^* chronic," as we now use them, are 

 not synonymous with the same terms as employed by dermato- 

 logists; that ice refer only to elementary lesions, and that an 

 exanthem, which might justly be included in the chronic 

 category of dermatologists, may really be made up of continual 

 repetitions of an acute inflammatory process. It is desirable 

 to guard against such misconceptions from the first. Even 

 at the risk of saying the same thing twice over, we will narrow 

 or extend the limits of the fundamental types of exanthematic 



