ON THE PATHOLOGY OF SHEEP-POX. 235 
highly refractive granule. The necklaces, which have 
grown to a great length and have become much con- 
voluted, are apt to break up into shorter chains, 
forming 
3. Groups from which the free ends of the filaments pro- 
ject. By the coalescence of these groups of convoluted 
chains, colonies, consisting of micrococci closely 
packed together, are produced, which correspond in 
appearance to the Zooglea of Cohn; these colonies 
are often connected together by 
4. Long filaments, some of which still show a necklace- 
like structure, while others are apparently smooth and 
homogeneous. ‘Twenty-four hours later the colonies 
were found to have increased in number and size ; 
some of the individual micrococci had also undergone 
changes, having not only acquired larger dimensions, 
but haying assumed the appearance represented in 
Fig. 1 (7). 
From the appearance above described I conclude that the 
highly refractive spheroid is the only form that can be re- 
garded as characteristic of the lymph of sheep-pox in its 
active condition. 
Sxcrion I1].— Anatomical Investigation of the Changes which 
occur at the Seat of Inoculation. 
1. The development of the primary pock may be divided 
into three stages, of which the first is characterised by pro- 
gressive thickening of the integument over a rapidly increasing 
but well-defined area; the second, by the formation in the 
rete Malpighii of vesicular cavities containing clear liquid 
(the “cells” of older authors), in which sooner or later 
organic vegetable forms are developed ; the third, by the im- 
pletion of these cavities with pus-corpuscles. It is to be 
noted that the division into stages is less marked than in 
human smallpox. 
2. The process commences in the rete Malpighii and in 
the subjacent papillary layer of the corium—in the former, 
by the enlargement and increased distinctness of outline of 
the cells, and by corresponding germinative changes in their 
nuclei; in the latter, by the increase of size of the papille, 
and by germination of the endothelial elements of the capillary 
blood-vessels. 
3. It is next scen that the interfascicular channels (lym- 
phatic canaliculi) of the corium are dilated and more distinct ; 
that the lining cells of these channels are enlarged and more 
