418 CONTAGIOUS PLEURO-PNEUMONIA IN CATTLE 
“From all appearances the contagious pleuropneumonia virus seems 
to have a specific action upon muscle and connective tissue, affecting 
chiefly the connective tissue elements. 
“The appearances suggest that the virus multiplies in the lymph 
spaces of the connective tissue and blood vessels, gradually working 
its way through the walls of the blood vessels, causing an inflammation 
of the intima and thus giving rise to thrombus formations. 
“The virus having invaded the tissue gives rise to a sero-fibrinous 
exudate, intermingled with groups of leucocytes leading to thrombosis 
of both lymph and blood vessels. 
“The muscle lesions correspond with the lung lesions of contagious 
pleuro-pneumonia in the following respects: 
(a) Thrombus formation in the veins in both tissues. 
(b) The inflammatory areas around the blood vessels are similar. 
(ec) The connective tissue is chiefly affected in both tissues. 
(d) The abundant serofibrinous exudate is present in both. 
(e) The deep staining line of leucocytes along the edge of the con- 
nective tissue is characteristic in both tissues. 
(f) The tendency toward a chronic productive inflammation is 
present in both. 
“Thus in summing up all the lesions one finds the lung and muscle 
lesions corresponding in practically every respect.” 
One of the most conspicuous features in a microscopic examination 
of a lung affected with acute contagious pleuro-pneumonia is the 
presence of intensely stained foci and lines. These lines, to which 
Welch seems to have been the first to call attention, are visible to the 
naked eye and when viewed with a hand lens suggest by their peculiar 
curves the contour lines of amap. They are situated at the margin of 
and within the inflamed connective tissue which surrounds the large 
vessels and separates the lobules from one another. A closer examina- 
tion of these lines indicates that they coincide with the boundaries of 
the lobules and of the individual lymph spaces of the interlobular 
tissue. Under a high power they are resolved into dense masses of 
leucocytes in various stages of degeneration. These dense bands are 
presumably attracted to the connective tissue boundary of the lobules 
and to the walls of lymph spaces within the connective tissue by the 
unknown cause of the inflammation, presumably the cause of the 
disease itself. The space between the lines is filled with fibrin, in 
which very few leucocytes are found. 
