348 
J. T. DUNCAN. 
Three very distinct conditions of the lnng tissues are to be 
noted : 1st, clear exudation ; 2d, opaque consolidation ; and 3d, 
black consolidation. 
The two latter forms, viz.: the opaque and black consolida¬ 
tion, are seen in various stages in the diseased lung, generally, 
however, if they co-exist, being sharply divided from each other 
by the pale markings spoken of previously. 
The portion of tissue showing the black consolidation are 
denser, heavier than the opaque, and show a further advanced 
and more intensely diseased condition. Around both the opaque 
and black portions, however, may be seen the first conditions 
spoken of, viz.: the clear exudation. 
This may be spoken of as simply exudate, and infiltrates the 
tissues with a clear material, found, as previously stated, in the 
periphery of the diseased portions, forming a very complete case 
around them. The three conditions spoken of now may seem to 
shade off into each other, but they are really distinct. The clear 
and opaque forms, also, may be seen without the black, but the 
latter is never found alone, being always associated with and pre¬ 
ceded by the other lesions, which seem to be of much longer dura¬ 
tion. 
The more important of the foregoing facts, as to the lung 
change, are: 
1st. The lung parenchyma is usually the seat of various forms 
of irregularly arranged exudation, which gives it a mottled look. 
2d. The interlobular spaces are always the seat of more or 
less exudation, which gives the sections the appearance of pale 
yellowish lines. 
3d. These pale lines sub-divide the mottled surface into irregu¬ 
lar small fields— marbling. 
4th. Three kinds of lung lesion— [a) Clear exudation; ( b) 
Opaque ; (c) Black consolidation. 
5th. (a) or (b) may become dense, and form tissues of cicatri¬ 
cial hardness. 
6th. (c) may produce gangrene, caseous degeneration or fibrin¬ 
ous crumbling. 
There remains now to speak only of the changes in the bron- 
