o66 MORBID ANATOMY OF THE SKIN. 



spindle-shaped variety, till tliey finally assume the shape of 

 ordinary pavement-Gells. Thus the summit of the growing 

 papilla is made up of embryonic cells passing externally into 

 epithelium, and internally into connective tissue — a sort of 

 '^ cambium " layer, such as exists in the stem of a plant between 

 the bark and the wood. 



§ 308. The common hard wart (Verntca) consists of a 

 circular group of elongated papilliie, with their free extremities 

 slightly enlarged and bulbous, their vessels dilated and extending 

 close up to the epidermic covering. The latter, in marked 

 contrast to ichthyosis, presents its normal threefold division, 

 inasmuch as a thick layer of transition-cells fills up all the 

 interstices between the enlarged papillaB, while the horny lamina 

 invests the entire group with a common covering. At a later 

 stage, when the wart attains an elevation of one line shove the 

 surrounding surface, the horny lamina exhibits rents and fissures 

 which correspond to the interstices between the enlarged papillae, 

 and which gradually penetrate to the base of the wart. We are 

 then able to see, without the aid of a lens, how many papilla) go 

 to make up the wart. Their number varies from three to 

 twenty and more ; the size of the wart varies accordingly, from 

 that of a pin's-head to that of a split bean. It seems, moreover, 

 as though this dismemberment of the wart were the first step 

 towards its spontaneous cure ; the admission of air into its 

 interior making the soft cells which it contains dry up together 

 with the papillae. 



From an etiological point of view it may be interesting to 

 know that the circular limit of the hyperplastic spot of skin 

 corresponds to the area of distribution of a vessel of variable 

 size. I can assert from personal observation that the very 

 small, flat, discrete warts to which Asclierson has given the 

 name of '^ Verruca? plana?," and which are usually met with on 

 the face and hands of adults, are often grouped in a manner 

 suggestive of the ramifications of a vessel. 



§ 309. The cauliflower excrescences or papillomata of 

 the skin, the smaller varieties of which are known as ^^ Porrum" 

 or " Acrothymion," diifer from ordinary warts in that their 

 constituent papillae are destitute of a common covering ; they are 

 isolated from the first, each papilla growing in some measure 

 independently. Their mode of growth resembles, upon the whole, 



