Yin; LI;N<; i'L.\<;rE OF CATTLE. 47 



of lung, Of if more extensive thai portion which covers sound lung tissue is much 

 more recent, :uid has probably been determined l>y infection from the liquid tlirown 

 out into t he chest. 



In the lung itself the most varied conditions are sjecn in different cases and at dif- 

 ferent Stages of the disease. The diseased lung is solid, linn and resistant, seems tit 

 he greatly enlarged because il tails to collapse like the healthy purl ion when the chest 

 16 opened, 18 greatly increased in weight and sinks in \vater. When cut across it 

 shows a peculiar linear ir.arking (marbling) due lo the excessive exudation into the 

 l-.ose and ahundant connective tissue \\ Inch separates the different lobules of the ox's 

 lunu 1'iom each other. This exudation is either clear, and therefore dart as seen by 

 reflected light, <>v it is of a yellowish-white and when filled with it the interlobular 

 tissue appears aa a net-work, the meshes of which vary from a line to an inch across, 

 and hold in its interspaces t he pinkish-gray, brownish-red, or black lung tissue. 



\Vheu only recently attacked the lung may present two essentially different appear- 

 ances: 



1. Most frequently the Changes are mo&l marked in the interlobular connective tis- 

 sue, -which is the seat of an abundant infiltration of clear liquid, while the lung tis- 

 sue, surrounded by this, retains its normal pinkish-gray color, and is often even paler 

 and contains less' blood than in health. It has, in short, become compressed by the 

 BUROtmding exudation, and air and blood have been alike in great, part expressed 

 from its substance. This extreme change in the tissue surrounding t he lobules and 

 the comparatively healthy appearance of the lobules themselves, have led many observ- 

 ers to the conclusion that the disease commenced in this connective tissue beneath the 

 pleura and extended to the proper tissue of the lung. There is, how ever, as pointed 

 out by Professor Yeo, a coexistent disease of the smaller air tubes corresponding to the 

 lobules that are circumscribed by this infiltration, and there is every reason to believe 

 that the infiltration in question is the result of antecedent changes in the air tubes. 



2. Less frequently we find the lobnles of the lung tissue presenting the first indica- 

 tions of change. The lobules affected are of a deep red and more or less shining, yet 

 tough and elastic. They do not crepitate on pressure, yet they are not depressed be- 

 neath the level of the adjacent healthy lung tissue as they would be if collapsed. 

 The interlobular connective tissue, devoid of all unhealthy exudation, has no more 

 than its natural thickness, and reflects a bluish tint by reason of the subjacent dark 

 substance of the lung. Here the lung tissue itself is manifestly the seat of the earliest 

 change congestion and the interlobular exudation has not yet supervened. Speci- 

 mens of this kind may be rare, but a number have come under the writer's observa- 

 tion, and in lungs, too, that presented at other points of their substance the excessive 

 interlobular exudation. 



Both of these forms show a tendency to confine themselves to particular lobules 

 and groups of lobules of the lung. They correspond, in short, to the distribution of 

 particular air tubes and blood vessels, as will be explained further on. The fact, how- 

 ever, is noteworthy as characteristic of this disease, that it attacks entire lobules, and 

 the limits of the diseased lung tissue are usually sharply marked by the line of connec- 

 tive tissue between two lobules, so that one lobule will be found consolidated through- 

 out, and the next one in a perfectly natural condition. 



The two forms just described differ also in cohesion and power of resistance. The 

 lung saturated with the liquid exudation has its intimate elements torn apart and is 

 more friable, giving way readily under pressure, while that in which there is red 

 congestion, but no extensive exudation, retains its natural elasticity, toughness, and 

 power of resistance. 



Hepatization. Another condition of the diseased lung tissue, more advanced than 

 either of those just described, is the granular consolidation or hepatization. In this 

 condition the affected regions of lung are as much enlarged as in the dropsical condi- 

 tion, but they are firmer and more friable, and on their cut surface present the ap- 

 pearance of little round granules. These granules are not peculiar to the lung tissue 

 proper, though most marked on this; they characterize the interlobular connective 

 tissue as well. They consist mainly of lymphoid cell growths, tilling up the air cells, 

 the smaller air tubes, the lymph spaces and the meshes of the connective tissue. The 

 color of the>e portions varies from a bright reddish-brown to a deep red, according to the 

 compression to which the lung tissues has been subjected by the exudation in the early 

 stages. 



Infarction. Another form of lung consolidation is of a very dark red or black, and 

 always implies the death of the portion affected. The dark aspect of the diseased lob- 

 nlesforms a strong contrast with the yellowish-white interlobular tissue, excepting in 

 eases where that also becomes blood-stained, when the whole presents a uniform dark 

 mass. This form has the granular appearance of that last described, and on micro- 

 scropic examination its minute blood-vessels are found distended to their utmost ca- 

 pacity with accumulated blood globules. This black consolidation is always sharply 

 limited by the borders of certain lobules or groups of lobnles which are ^connected 



