350 MOHBID ANATOMY 0¥ THE SKIN. 



must be remembered that the small-pox papule differs very 

 essentially from the papules we have already described (e.g. the 

 papule of measles). The small-pox papule is situated, at least in 

 great paii, in the substance of the epidermis, not underneath it. 

 It begins, apart from the hyperaemic condition of the papillary 

 body, as a circumscribed "parenchymatous inflammation" of 

 the epidermis. I use this word under reserve. That peculiar 

 <:loudiness and swelling of the cells which was discussed in § § 36 

 and 37, and which meets us here once more, has not in my 

 opinion established itself on a very firm footing, as yet, in 

 general pathology. The circumstance that the swelling leads as 

 often to fatty degeneration as to endogenous multiplication, 

 renders it doubtful whether it ought to be considered as a pro- 

 gressive or as a retrograde metamorphosis of cells. The present 

 ease is undoubtedly one of incipient productive activity, whicli 

 may therefore rightly be called "inflammatory." 



It is neither in the deepest nor in the most superficial layer 

 of the epidermis that the swelling begins ; its starting-point is 

 in the middle strat:im, which we have already described as com- 

 posed of " intermedi.ite cells," and as belonging to the mucous 

 layer. These cells are no longer naked, like those smaller 

 elements which are in immediate contact with the papillary 

 body ; they possess a membranous investment whose surface 

 already exhibits here and there that delicate grooving which was 

 first discovered by M. Schultze. The presence of a limitary 

 membrane renders it impossible for them to respond to the 

 inflammatory stimulus by simple fission ; their proliferation 

 must take place by endogenous development. But the first 

 stage of endogenous growth is that same " cloudy swelling " 

 which is followed by segmentation of the enlarged protoplasm 

 and the transformation of the " segmentary sj^heres " into 

 pus-corpuscles (cf the description in § QSj fig. 30). 



§ 296. The shape of the individual pock is always circular ; 

 more complex forms are always due to the confluence of adjoin- 

 ing papules. This j^culiarity, as may be shown in the case of 

 many pocks, is due to a concentric arrangement of their ele- 

 ments round the orifice of a hair-sac or sweat-gland. These 

 pocks may be distinguished from the rest even with the naked 

 eye. They exhibit a central depression, the " umbilicus." 

 Everybody knows that both the rete Malpighii and the 



