246 
DE. E. KLEIN ON THE SMALLPOX OE SHEEP. 
of some of the cells rows of highly refractive granules may be seen. 
These granules become fewer and smaller as they approach the middle 
layers, C, of the rete Malpighii, and eventually disappear. Many of 
the nuclei of the epithelial cells of the middle layers and of the lower 
layers, D, are seen to be divided. In D some of these divided nuclei 
are vacuolated or dropsical. In the middle layers epithelial cells may 
he seen, both isolated and in groups, which are sharply defined and 
opaque. These are being converted into a homogeneous horny 
substance. 
PLATE 30. 
Fig. 5. Vertical section of half of a pock, excised seven days after its appearance, 
showing a pale central and a thickened reddish peripheral part. The figure 
shows the general distribution of the infiltration. (Oc. 3. obj. 2.) 
A. Part of the pustule where the peripheral thickening is in contact with 
healthy tissue. 
B. Epidermis of healthy skin. 
C. Epidermis of central part of pustule, showing the rete Malpighii divided 
into three layers — a superficial layer composed of nucleated somewhat 
flattened cells, a middle, horny layer, and a lower layer composed of 
polyhedral, nucleated, granular epithelial cells, the true rete Malpighii. 
(Compare with fig. 6.) 
D. Superficial layer of corium, showing infiltration with lymph-cells around 
the blood-vessels and in the lymphatics. 
E. Deep layer of corium, containing sebaceous and sweat-glands. 
F. Superficial layer of subcutaneous tissue, showing the interfascicular 
lymph-channels much distended. The smaller branches of the 
canalicular system could not be represented, owing to their extreme 
minuteness. 
G. Deep layer of subcutaneous tissue, showing fat-cells and transverse 
sections of blood-vessels and lymphatics. 
It will be observed that infiltration with lymph-cells occurs abun- 
dantly at the periphery of the pustule, and extends through all the 
layers, but chiefly in the corium and deep subcutaneous tissue. 
Fig. 6. Vertical section of central depression of a primary pustule seven days old, 
showing the changes in the epithelium. (Oc. 3, obj. 7.) 
A. Horny layer. 
B. Superficial layers of rete Malpighii undergoing conversion into horny 
scales. 
C. Deep layers of rete, composed of protoplasmic, germinating epithelial 
