DR. E. KLEIN ON THE SMALLPOX OE SHEEP. 
235 
be seen in many places that the mycelium extends from the lymph-canalicular system 
into the neighbouring lymphatic vessels in which their ends are provided with the 
conidia. 
In fig. 11, in A & B for instance, the mycelium-filaments, from the terminations of 
which spring the conidia seen in the lymphatic vessel, can be traced for a long distance 
into the 1-ymph-canalicular system, from which the lymphatic vessel receives its supply. 
Not only does the fungus extend from the tissue into the lymphatic vessels, but also 
into some veins ; for I have seen several instances where one could trace the mycelium 
from the interfascicular spaces into the veins, containing filaments in a state of fructifi- 
cation similar to that observed in lymphatic vessels (fig. 10, V.). The mycelium and 
its conidia-bearing parts are most easily seen, and with the greatest distinctness, 
in the distended lymphatics, where they are found in immense numbers, and sometimes 
form a very dense thallus. They are, however, seen to extend 'all through the tissue of 
the corium — in the earlier stages, as mentioned above, only in the deeper stratum of the 
corium ; later also in the superficial stratum of the corium and the subcutaneous 
tissue. In the latter the fructification is seen in the later stages to go on with such 
rapidity that the distended interfascicular lymph-spaces at some parts become filled with 
a zooglcea-like mass, in which here and there the minute spores, the products of division 
of the spores previously mentioned, can be still recognized to form necklace-like chains. 
In Plate 32. fig. 13 this zooglcea is represented in lymphatic vessels and in the inter- 
fascicular spaces of the subcutaneous tissue. 
We return now to the structural changes in the skin of the pock. In pocks which 
have been cut out two to three days after their appearance, the rete Malpighii is seen 
to be many times thicker than in the normal parts, and thickest in the centre. The 
cells of the deeper and middle strata are enlarged and sharply outlined. Many of them 
are in the condition of multiplication, as may be deduced from the fact that they possess 
two nuclei, and that, particularly in the deepest layer, the nuclei are much closer to 
each other, i. e. more numerous. In the flattened cells of the more superficial strata there 
lie close to the poles of the oblong nucleus highly refractive granules, which are largest 
and most numerous in the most superficial cells, and become smaller and scarcer in the 
deeper strata ; at the same time the nuclei of many cells of the superficial strata look 
as if they were vacuolated, viz. sharply outlined with perfectly clear contents. 
At the central parts of the pock the rete Malpighii shows other important changes : 
isolated epithelial cells, or, as is oftener the case, small groups of two, four, or a greater 
number, are met with, which differ from the rest in containing much coarser granules 
and possessing very distinct sharp outlines ; they are at the same time always more or 
less rounded : in some of them the nucleus is double or is in the act of division ; 
these occur chiefly in the middle strata of the rete Malpighii. Amongst them some 
are seen to be darker and more homogeneous than the rest, so that their nuclei are 
hardly or not at all visible ; while others appear to have become confluent, so as to give 
rise to the appearance of dark more or less homogeneous horny streaks of longer or 
