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DR. E. KLEIN ON THE SMALLPOX OF SHEEP. 
pigment-granules on a warm stage and creep away with them. As the rete Malpighii 
becomes infiltrated with lymph-corpuscles, they appear to be eliminated from the corium ; 
for I have preparations of pocks in which, while the very abundant cavities in the 
rete Malpighii are crammed with lymph-corpuscles, the papillary tissue has become 
almost barren of them. 
In one instance I have had opportunity of observing a primary pock in which an 
enormous infiltration of the corium with lymph-corpuscles, and the formation of very 
numerous pustular cavities containing them, had taken place at a relatively very early 
period, the fourth or fifth day after its appearance. In this case the deepest stratum 
of the rete Malpighii at the periphery of the pock was actually completely broken 
through by the contents of the papillae, whereby a broad direct passage was established 
between the latter and the intercommunicating pustular cavities. In primary pocks 
of old standing, when the formation of the vesicles and their infiltration with lymph- 
corpuscles has reached a very high degree, the layers of the rete Malpighii containing 
the vesicles nearest the surface are seen to become very much loosened from the sub- 
jacent strata of the rete and to detach themselves easily. In this stage, when the 
papillae contain few lymph-corpuscles, there are found, in the matrix of the papillae 
(which is now transparent, finely granular, or homogeneous), more or less sinuous large 
spaces very close to the rete Malpighii, which contain a clear lymph and occasionally 
also masses of Micrococci. These spaces enlarge into the rete, and may even become 
continuous with the deepest vesicles. 
I have now only to add a few words relating to the other parts of the skin. 
Of the glands of the corium the sebaceous glands deserve the most attention. The 
epithelium of the glands and their ducts (properly speaking the mouths of the hair- 
follicles) become immensely enlarged, chiefly on account of their epithelium proliferating 
so enormously that it is composed, like that of the rete Malpighii, of a very great number 
of layers. The deepest epithelial cells, the nuclei of which are rapidly dividing and 
many of them in a state of vacuolation, become smaller and smaller and at the same 
time more loosely connected with one another. 
In the ducts the epithelial cells which are nearer to the lumen are, on the other hand, 
more swollen, more transparent, and dropsical. The infiltration of the rete Malpighii 
with pus-corpuscles extends into the mouth of the sebaceous gland and also into the 
proper secretory parts of the glands. The pus-corpuscles of the surrounding tissue 
gradually penetrate amongst the epithelium of the former to such an extent that the 
centre of the gland in some places becomes completely filled with closely packed pus- 
corpuscles. 
Although there is a marked infiltration of the sweat-glands with pus-corpuscles from 
the surrounding tissue, this infiltration never reaches such an extent as in the sebaceous 
glands. The epithelium of the sweat-glands becomes more and more loosened under 
the infiltration, and the lining epithelial membrane becomes broken up into a number 
of small cells, the nuclei of most of which show vacuolation. 
