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the normal type. Thus very minute lesions of the epidermis are found . 
in which no more than three or four cells show marked change. (PI. IV, 
fig. 21.) Some of the cells which have wandered into the epidermis are 
in a state of good preservation and these often contain eosin-staining 
nuclear inclusions similar to those which occur in the epidermal cells. 
Others present various degrees of degeneration and many have become 
disintegrated. The small masses resulting from their disintegration may 
consist of either nuclear or cytoplasmic material, or both, and are readily 
distinguished. 
The cell changes in the epidermis following the initial swelling are 
progressive. ‘T'wo types may be distinguished. In that termed by Unna 
“reticulating colliquation,” either the interior of the cell liquefies or a 
space is formed within it, while the periphery persists as a dense mem- 
brane. Within such hollow cells the nuclei are often collapsed, a condi- 
tion possibly produced by changes in the surrounding cell fluid. This 
form of degeneration is not so prominent, in the varicella lesion, as that 
next to be described. 
The term “ballooning degeneration” is given by Unna to certain 
changes resulting in the formation of large multinucleated cells with 
soft plastic cytoplasm. The first change is an increase in the size of the 
celle while the nucleus becomes large and vesicular; the nucleus then 
divides by direct division, and this process is rapidly repeated until a 
large number of nuclei are produced within the cell. The cytoplasm is 
basophilic, and in it a distinct reticulum appears. The limiting mem- 
brane and protoplasmic bridges of the cell become less distinct and after 
a time disappear. Such cells attain enormous dimensions. The nuclei 
are usually grouped in the centre of the cell, often so closely packed 
together that the opposing surfaces are flattened one against the other. 
These nuclei appear as hollow sacs with one or several masses of chro- 
matin peripherally situated, and with an eosin-staining inclusion in the 
interior of each nucleus.* There is scarcely any indication of a nuclear 
network. In the presence of such a degree of amitotic division, it is 
nevertheless difficult to find nuclei caught in the act of division. The 
chromatin in some instances projects as a septum nearly across the 
nucleus. The dividing split passes directly through this projecting 
chromatin so that an approximately equal portion goes to each of the 
resulting nuclei. Although this would seem, from the common occur- 
rence of nuclei flattened against one another, to be the common form 
of direct division, yet it can not be considered to occur constantly in this 
process. Certain nuclei are dumb-bell shaped and the two portions are 
joined by a very thin filament. Some are lobulated and are apparently 
in the process of constricting off small portions of their substance which, 
form accessory nuclei of varying size. This latter form of nuclear divi- 
sion is seen in a greater degree in the migrating cells and in the endo- 
thelium lining the lymphatics of the corium, than in the epithelium. 
