, ana 
Medes Me | re Ph * ae ty oe ew es Aa” QIN i: a ae a 
357 
- skin before excision, sometimes used, is very objectionable. The blood is. 
destroyed and the tissue cells are so altered that the subsequent staining 
is affected. 
The tissue was generally fixed in Zenker’s fluid. Lesions were excised 
twelve hours, one, two, three, four, five, six, and seven days after the 
eruption was first noted by the patient.. On account of the appearance 
of successive crops of vesicles, it was often possible to obtain early lesions 
late in the disease so that the time interval, dated from the first appear- 
ance of the eruption, forms no index as to the stage of the process present. 
In order to acquire a more accurate knowledge of the development of the 
lesions, certain ones were ringed with indelible ink at their first ap- 
pearance and the subsequent changes noted. 
The following description of the process is based on a study of a 
series of lesions of the type which appears most constant, beginning with 
the earliest recognizable stage and taking up successive stages until repair 
is well advanced. In such a series of lesions the process is found to 
consist of changes occurring simultaneously in both epidermis and corium. 
However, for purposes of description, first the changes affecting the 
epidermis and subsequently the changes affecting the corium will be 
discussed. ‘The same order will be followed in the description of the later 
changes which result in the repair of the skin lesions. Following this 
the more unusual forms of the lesion will be described separately. 
The earliest lesions are obtained by the excision of red spots which 
precede the formation of vesicles. The first change in the epithelial cells 
consists of a swelling both of the cytoplasm and of the nuclei so that the 
epidermis is considerably thickened over a small area. (Pl. I, fig. 1.) 
The process in the epidermis is ofeten not confined to a single center. 
It is common to find multiple distinct centers separated by normal 
epithelium, and multiple centers which merge one into another forming 
a conglomerate lesion. (PI. I, fig. 2.) With the swelling of the cells 
the cytoplasm stains more faintly and becomes distinctly reticulated. 
The nucleus is also distended so that it appears large and hollow. These 
nuclei almost invariably contain one or several masses of eosin-staining 
material. The nuclear network and the chromatin masses are retracted 
away from this material so that it appears to occupy a clear space 
within the nucleus. There are constantly present in addition to the 
nuclear inclusions, small deeply staining, rounded masses, situated on the 
outer surface of the nuclear membrane, in the cytoplasm, or between the 
epithelial cells. A discussion of the céll-inclusions associated with this 
process will be taken up in a subsequent paragraph. 
Foreign cells occur here and there in the affected areas of the epidermis. 
.From the study of the changes in the underlying corium, it seems prob- 
able that these are cells of endothelial origin which have migrated into 
the epidermis. In many instance these extraneous cells are found in 
portions of the epidermis where there are but few cells deviating from 
