340 MOKBID ANATOMY OF THE SKIN. 



points of the cutaneous surface which lie within its area ; and in 

 proportion as this occurs, we may anticipate further changes of 

 an inflammatory kind at these points. 



§ 289. — 2. The pajndar exantliem. By a papule we under- 

 stand a slight elevation of the cutaneous surface, which feels 

 like a little solid nodule seated on the skin. The papule 

 originates by the passage of an inflammatory hyperemia into 

 exudation, w^ithin a limited area of the papillary body. The 

 exudation is not situated in the epidermis. This stretches 

 unaltered over the enlarged papillae ; it is more tense and 

 elastic than usual owing to its extension over a larger area. 

 The exudation is situated in the substance of the papillf:e. 

 They are saturated with an abundant supply of nutrient fluid — 

 not with cells (at least in recent cases). We shall find here- 

 after that formative changes are superadded when the papule ha& 

 lasted for some time, and especially if it proceed to become a 

 pustule. The individual papilli^ are markedly enlarged. It has 

 been asserted that they undergo, not so much an elongation and 

 thickening at their apices, as an expansion at their bases, so that 

 the level of the surface is in some sort depressed within the area 

 of infiltration. This assertion hardly admits of proof or disproof, 

 inasmuch as any direct observation is as good as impracticable. 

 For, like many other infiltrations of the connective tissue, this infil- 

 tration disappears during or immediately after death. The elastic 

 reaction of the stretched cuticle drives the exuded fluid back 

 into the vessels as soon as the cessation of the vis a tergo allows 

 it to do so. We find patches of skin which, a short time before, 

 exhibited the eruption in all its distinctness, apparently quite 

 healthy. For my own part, I believe that the shai'ply circum- 

 scribed character of the papular elevations points rather to a 

 turgescence of the slightly bulbous tips of the papillae. The 

 affection is very prone to select the ring of small, closely- 

 set papillae which surrounds the orifices of the hair-follicles. 

 Such papules are circular in outline, of considerable size, and 

 perforated at their centres by a hair. Hehra assumes that in 

 these cases a minute quantity of fluid is previously exhaled 

 between the horny and the mucous layers of the epidermis. 

 Here too I must say that I failed to discover any fluid in the 

 substance of the epidermis ; but the point does not seem to me of 

 much moment. 



