MINUTE ANATOMY OF EPIDERMIS IN SMALLPOX OF SHEEP. 393 



Contribution to the Minute Anatomy of the Epidermis 

 in Smallpox of Sheep. By E. Klein, M.D., F.R.S 

 (With Plate XXIV.) 



In my paper ou slieep-pox ("Research on Smallpox of 

 Sheep," ' Philosophical Transactions/ vol. 165, 1874) I have 

 shown that in the thickened epidermis of the primary pocks 

 — i. e. those produced directly at the seat of inoculation — a 

 peculiar change takes place in the rete Malpighii, which leads 

 to the formation of what 1 called a median horny streak. I 

 have shown that in the middle layers of the greatly hyper- 

 trophied rete Malpighii smaller or larger groups of epithelial 

 cells are converted into horny, irregular masses, the nuclei 

 of the cells at the same time disappearing. By the confluence 

 of a number of such horny masses there is formed a stratum 

 in thereto Malpighii, which corresponds, in all its characters, 

 to the stratum lucidum, i. e. the deep portion of the stratum 

 corneum. By that additional stratum lucidum thereto Mal- 

 pighii is separated into two sections, a deej) one representing 

 the true rete Malpighii, and an upper or superficial one, 

 situated between tlie two strata lucida (see ' Philosophical 

 Transactions,' Plate 30, fig. 6 ; Plate 32, fig. 14 ; and also 

 this memoir, Plate XXIV, fig. 3). The cells of the latter 

 become, however, gradually homogeneous ; their nucleus 

 diminishes in size and also in the power of taking up stain- 

 ing until it is altogether lost; the cell outlines disappear, 

 and the whole mass becomes eventually one with the stratum 

 lucidum. In consequence of this change the two strata 

 lucida, i.e. the true stratum lucidum and the additional or 

 median stratum lucidum (median horny streak), become 

 fused into one thick layer. This change I have shown to 

 take place first in the middle of the pustule, and gradually 

 to spread towards the periphery. 



In the sixty-ninth volume of ' Virchow's Archiv,' p. 409 

 (March, 1877), Dr. Unna describes, in the smallpox of man, 

 a structure in the epidermis of the pustule, which he calls 

 " Pockenkorper,'^ and which so closely resembles our upper 

 section of rete Malpighii enclosed between the two strata 

 lucida (see Plate XXIV, fig. 3), that I have no doubt the 

 two are in their structure and development identical. Dr. 

 Unna, however, gives a totally different account of the de- 

 velopment of the "■ Pockenkorper" in smallpox of man from 

 the one I gave of the analogous structure in the sheep-pox, 

 and he assigns to the " Pockeukorper" such an importance 



