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DR. E. KLEIN ON THE SMALLPOX OF SHEEP. 
The pustular contents are enclosed, as if by a capsule, by two layers of unnucleated 
epidermic cells. Besides the pus-cells there are also unnucleated elements (insoluble in 
acetic acid) with fine granular contents. 
Auspitz and Basch are of opinion that the so-called umbilicus of the pock, the cen- 
tral depression, is due to the pustule gradually extending towards the periphery, whereby 
the pressure in the centre diminishes and the central part becomes depressed. 
According to Rindfleisch and others, on the other hand, the central umbilicus is pro 
duced by there being a sweat-duct or a hair-follicle in the centre of the pock, which, 
when the pustule is formed in the epidermis, keeps the latter fixed to the corium like a 
retinaculum*. 
B. Anatomical Peculiarities of the Skin of the Sheep. 
Before I describe the pathological changes of the skin, I will draw the attention of 
the reader to several anatomical points, as regards the structure of the skin of the sheep, 
which have not been properly described yet. 
(a) In the skin of most parts of the body (e. g. groin, wall of abdomen and chest, 
axilla, and so on) the epidermis (stratum corneum plus rete Malpighii) is in hardened 
preparations thin and rather opaque — only the deepest, or at most this latter and the 
next stratum, appear to be composed of cells elongated vertical to the surface ; the other 
layers of the rete Malpighii are composed of more or less polyhedral cells, which are 
the more flattened the nearer to the surface. In general the outlines of the cells are 
very indistinct ; the whole rete Malpighii looks more like an opaque granular substance, 
in which nuclei are imbedded in more or less definite intervals. 
( b ) The papillae of the corium are very scarce, short, and small ; in many places the 
rete Malpighii rests on a corium, the surface of which is only slightly wavy, i. e. the 
papillae are only just indicated. 
(c) The corium may be divided into a superficial stratum, which includes the papilla 
and the tissue directly underneath it, and a deep stratum beneath the former, containing 
the sebaceous glands, sweat-glands, and the roots of the hair-follicles. 
The superficial stratum is a dense connective-tissue feltwork with numerous elastic 
fibres ; it contains the ultimate ramifications of the blood-vessels and lymphatic vessels. 
The deep stratum is somewhat looser in its structure than the former, but is still 
similar to it, as the connective-tissue bundles of its matrix are very small, run in all 
* If the central depression I have mentioned in the primary and some secondary pocks of sheep in Section I. 
correspond to what is described as the umbilicus of variola of man (and to all appearance they do correspond 
to each other), then I must anticipate so far as to say that this central depression has no connexion whatever 
either with the formation of the pustule or with the hair-follicles or sweat-ducts, hut, as we shall see hereafter, 
is due, to a great extent, to certain morphological changes of the epidermis in the centre of the pock. In 
Luginbuhe’s paper, quoted above, I find, on p. 160, a reference to Auspitz and Basch, Neumann, and Cornie 
having found Micrococci in the meshes of the fully developed pustule and also in the corium ; and, finally, 
C. Weigert describes (Centralblatt der medicin. "Wissensch. 1871, No. 39) sinuous tubes in the corium of 
smallpox, which tubes (lymphatic vessels) are filled with Micrococci. 
