182 Report on the Pathological Anatomy of.Pleuro-pneumonia. 
has much in common with that which is brought about by other 
causes, it differs materially from the hepatisation caused by 
ordinary pneumonia in man, and these differences form its chief 
diagnostic characters. The dense solidity is seldom accompanied 
by any friability of the tissue, but is resisting and elastic, except 
in those parts where the tissue is undergoing necrosis. Such 
circumscribed localisation and boss-like swelling only occur, as 
far as I know, in this disease and in malignant growths. The 
manner in which the different changes in colour are distributed 
forms another striking characteristic. There never is any 
gradual shading of one colour into another, as seen in the acute 
pneumonia of the human lung, but the different shades are placed 
side by side, being separated by most abrupt lines. The greatest 
possible varieties of shade may be seen irregularly distributed in 
patches of various sizes ; here and there a dull buff colour, or a 
bright crimson, mixed with deep brown or black. The normal 
pale pink colour of the lung is always lost, being replaced by 
some of the above shades, often arranged so as to produce a 
variegated or mottled appearance of the cut surface ; or a large 
black area may exist in the centre of the section through the 
diseased lobe, and this is commonly surrounded by patches of 
brown or buff. 
Perhaps the most striking appearance seen on the cut surface 
is the network of pale yellow lines which is distributed over it. 
The lines forming this network are, on an average, about one- 
eighth of an inch in diameter, always very pale, and sharply 
defined. They intersect and cross one another, so as to map 
out the surface into a number of polygonal areas, about half or 
three-quarters of an inch in diameter. These areas are found to 
correspond with the sections of the lobules, and the pale lines 
are obviously the swollen interlobular spaces cut across, the 
narrow lines which exist in the healthy lung between the 
lobules being represented by masses of more or less solid 
exudation, so as to give a cross-section of more than an eighth 
of an inch. This set of pale streaks, crossing the surface in 
many directions, reminds one of the whitish veins running 
through variegated marble ; and hence the common nam6 which 
has been applied to the appearance of the section of the lung 
lesion. This " marbling " is considered to be the great dia- 
gnostic character of the disease. 
When examined more closely, the increase in diameter of 
the interlobular partitions is found to depend on extreme filling 
of the tissue interstices and lymph channels with a material, 
which may be a clear fluid, or a translucent jelly j or, in the 
very advanced stages, a dense fibrinous mass may occupy -the 
entire space. 
