1874.] Dr. E. Klein on the Smallpox of Sheep. 389 



of the sheep, with special reference to those particulars in which it differs 

 from that of man. 



The remainder of the paper is occupied with the investigation of the 

 changes which occur in the integument at the seat of the inoculation, and 

 with the anatomical characters of the secondary pustules. 



The most important results are the following : 



1. The development of the primary pock may be divided into three 

 stages, of which the first is characterized by progressive thickening of the 

 integument over a rapidly increasing but well-defined area ; the second, by 

 the formation of vesicular cavities containing clear liquid (the " cells " 

 of older authors) in the rete Malpighii ; the third, by the impletion of 

 these cavities with pus-corpuscles and other structures. It is to be 

 noted that the division into stages is less marked than in human small- 

 pox. 



2. The process commences in the rete Malpighii and in the subjacent 

 papillary layer of the corium in the former, by the enlargement and in- 

 creased distinctness of outline of the cells, and by corresponding germi- 

 native changes in their nuclei ; in the latter, by the increase of size of the 

 papillae, and by germination of the epithelial elements of the capillary 

 blood-vessels. 



3. It is next seen that the interfascicular channels (lymphatic canali- 

 culi) of the corium are dilated and more distinct ; that the lining cells of 

 these channels are enlarged and more easily recognized than in the 

 natural state ; and that, in the more vascular parts of the corium, the 

 channels are more or less filled with migratory, or lymph, corpuscles. At 

 the same time, the lymphatic vessels, of which the canaliculi are tribu- 

 taries, can be readily traced, in consequence of their being distended with 

 a material which resembles coagulated plasma. 



4. About the third day after the appearance of the pock, the contents 

 of the dilated lymphatics begin to exhibit characters which are not met 

 with in ordinary exudative processes. These consist in the appearance, 

 in the granular material already mentioned, of organized bodies, which 



neither belong to the tissue nor are referable to any anatomical type 



viz. of spheroidal, or ovoid, bodies having the characters of micrococci and 

 of branched filaments. These last may be either sufficiently sparse to be 

 easily distinguished from each other, or closely interlaced so as to form 

 a felt-like mass. 



5. The process, thus commenced, makes rapid progress. After one or 

 two days, the greater number of the lymphatics of the affected part of 

 the corium become filled with the vegetation above described ; and on 

 careful examination of the masses, it is seen that they present the cha- 

 racters of a mycelium, from which necklace-like terminal filaments spring, 

 each of which breaks off, at its free end, into conidia. In most of the 

 filaments, a jointed structure can be made out, and, in the larger ones, the 



