VESICLE. — BULLA. Mt 



alluded to is stripped from the papillae, while remaining attached 

 to the bottom of the furrows. A system of cellular membranes 

 and trabeculsD is thus formed ; these structures extend more 

 or less vertically across the interval between the horny layer 

 and the papillary body; the thickest ones spring from the 

 interpapillary fissures ; they grow more and more slender in 

 proportion as they recede towards the summit of the papillary 

 elevations. These trabeculse are all made up of nucleated " in- 

 termediate " cells, which have been stretched and flattened out 

 mechanically. The thinnest bands consist of single cells, often 

 drawn out into several processes. If the transudation is more 

 copious, the trabeculce, whatever their size, are torn across, one- 

 half adhering to the detached horny layer, while the other is 

 retained by the papillary body. 



It is only in miliary vesicles that the fluid is contained be- 

 tween the layers of the horny lamina {HaigJit) ; but the intimate 

 connexion of this exudation with the perspiratory secretion 

 makes us hesitate before reckoning miliaria among vesicular erup- 

 tions at all. The fate of the vesicles is different in different 

 cases ; they may burst and discharge their contents, or they may 

 remain stationary until the hypersemia remits and allows the 

 exuded fluid to return to the blood. The pressure of the 

 stretched homy lamina, whose elasticity is well known, may 

 contribute to the latter issue. That this force ought really to be 

 taken into account, is plain from a consideration of blebs with a 

 hypersemic areola. In these, the contents of the bleb compress 

 the underlying vessels to such an extent, that the afflux of blood 

 is checked, and stagnation consequently occurs at the margin of 

 the bleb. The strata of epidermis which have once been sepa- 

 rated cannot however reunite. Even when the horny lamina is 

 closely applied to the underlying stratum, and the status quo 

 ante has apparently been re-established, we still find that the 

 affected lamellae wither and are shed before their time. Mean- 

 while a new homy lamina is developed at the expense of the 

 rete Malpighii. This continues abnormally thin for a long 

 period ; the vessels of the papillary body shine through it so 

 brightly that the size and shape of the former bleb may be 

 recognised for weeks and weeks as a red spot. 



The histological details of this renewal — what part of the 

 papillary body is mainly instrumental in the process, how strati* 



