PL^STULE. — SMALL-POX . 351 



lioruy layer of the epidermis are prolonged into the hair- 

 sacs. Now if the swelling — or still more that serous 

 saturation of the rete Malpighii of which I am about to 

 speak — extends to the circumference of the follicular orifice, 

 then the horny epidermic lamina which lines the follicle 

 (the inner root-sheath) will act upon the enlargement as a 

 central retinaculum (or bridle) ; and will thus prevent the 

 middle of the pock from rising to the same height as its peri- 

 phery. The epithelium which lines the ducts of the sweat- 

 glands is less tough than the inner root-sheath of the hair-sacs. 

 It owes what cohesive j^ower it has to its being stratified in a 

 plane which cuts that of the cuticular strata at right angles or 

 obliquely. But the morbid change does not even involve the 

 parts in immediate contact with the duct. At all events I have 

 many specimens in my possession which exhibit the ducts of 

 sweat-glands with the tissues immediately surrounding them as 

 the retinacula of smallpox papules (fig. Ill, a).* 



g 297. The next step in the developmental process is the 

 conversion of the papule into a pustule. This is invariably 

 preceded by a serous infiltration of the epidermis. A clear 

 fluid forces its way up from the papillary body, and raises the 

 horny lamina of the cuticle ; it does not detach it from the 

 mucous layer as in the production of a vesicle, but forces itself 

 between the lamellce of the latter structure, pushing them 

 asunder, and displacing them to such an extent, that from 

 having been horizontal they come to occupy an oblique or 

 vertical position (fig. Ill, h). This gives the upper part of the 

 pock a chambered ap2:>earance, which has long attracted the 

 notice of pathologists and has induced many to ascribe a loculose 

 structure to the entire pock. This is decidedly incorrect. It is 

 only the upper portion, the " dome " of the pock, which is 



* Aasjjitz aud Basch {Vlrclioiv's Arcliiv xxviii.) explain the umbilica- 

 tion of tlie pustule in a way wliicli does not seem to me very plausible : 

 '•' The swelling of the individual cells keeps^ extending in all directions 

 from the affected centre ; consequently the efflorescence as a whole, 

 increases in bulk ; the formation of pus in its centre proceeds but slowly 

 at first, and the pus is enclosed by the peripheric accumulation of 

 sv7ollen cells as by a capsule; the latter growing continually larger, 

 without the pus-formation in its interior being able to keep pace 

 with it." 



