230 
DK. E. KLEIN ON THE SMALLPOX OE SHEEP. 
(/) The large lymphatic trunks, situated, as mentioned above, in the deep stratum of 
the subcutaneous tissue, are provided with valves ; they form rich anastomoses, and 
stand in direct connexion with the intercommunicating system of the interfascicular 
spaces, i. e. lymphatic spaces of the deep and superficial stratum of the subcutaneous 
tissue. The interfascicular spaces contain the connective-tissue corpuscles ; that is to say, 
the latter are so fixed upon the connective-tissue bundles that the interfascicular spaces 
appear to be lined by the connective-tissue corpuscles. The deep stratum of the 
corium -contains the greatest number of lymphatic vessels ; they have chiefly a course 
parallel to the surface ; they are provided with valves, and stand everywhere in direct 
connexion with interfascicular spaces lined by the connective-tissue corpuscles. The 
lining membrane of the lymphatic vessels, composed of a continuous layer of endothe- 
lium, is therefore in direct continuation with the latter. The interfascicular spaces 
of this and of the superficial stratum of the subcutaneous tissue are in many places 
very much enlarged, and resemble lymphatic sinuses or lymphatic sacs, through which, 
in many instances, the smaller branches of blood-vessels are seen to penetrate — perivas- 
cular lymphatics. These lymphatic sinuses are especially well developed around the 
sebaceous glands at the bases of the arrectores pili, and also around the proper sweat- 
glands. Into the plexus of lymphatic vessels which lie in the deep stratum of the 
corium lead lymphatic vessels which come from the superficial stratum of the corium ; 
they are also provided with valves, and can be traced up to the papillary layer. Many 
of the lymphatic vessels of the superficial and deep stratum of the corium are seen to 
be in close relation to the blood-vessels, especially the veins, as they always seem to 
run with each other. 
C. Early Stage of the Development of the Primary Pustules. 
As has been already stated, the pocks designated as primary were excised in their 
different stages of development up to the period of pustulation, for anatomical exami- 
nation. The latest stage ( stadium exsiccationis) has not been particularly investigated, 
as it does not differ from any other restitutory process of the skin. In examining pocks 
in the earlier stages, I have usually cut up the whole into microscopic sections. Of the 
more advanced pocks I have examined sections of only one half. 
Sections through the primary pocks which had appeared only several hours (six to 
twelve) show as the most characteristic features the following: — The epidermis has 
markedly increased in thickness, chiefly due to an increase of the thickness of the rete 
Malpighii. The cells of the latter are more transparent and larger, their outlines more 
distinct than in the normal condition ; the cell-substance is finely granular ; the nuclei 
are enlarged, each possessing one or, more generally, two distinct nucleoli. The differ- 
ence in size, distinctness, and transparency of the rete Malpighii is very striking at the 
point where the skin of the pock is in contact with healthy skin. The cells of the three 
deeper strata of the rete Malpighii are elongated in a direction vertical to the surface. 
The papillae are much more distinct in the corium of the pock than in that of the 
neighbouring healthy tissue ; they appear broader and longer. The blood-vessels of 
