48 The Lung Plague of Cattle. 



while tlie lung tissue, 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, be- 

 come compressed by the surrounding exudation, and air 

 and blood have been alike in great part expressed from 

 its substance. (See Heliotype.) This extreme change 

 in the tissue surrounding the lobules and the compara- 

 tively healthy appearance of the lobules themselves, 

 have led many observers to the conclusion that the dis- 

 ease commenced in this connective tissue beneath the 

 pleura aad extended to the proper tissue of the lung. 

 There is, however, as pointed out by Professor Yeo, a co- 

 existent 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 lobules of the lung 

 tissue presenting the first indications of change. The 

 lobules affected are of a deep red and more or less shin- 

 ing, yet tough and elastic. They do not crepitate on 

 pressure, yet they are not depressed beneath the level of 

 the adjacent healthy lung tissue as they would be if col- 

 lapsed. The interlobular connective tissue, devoid of all 

 unhealthy exudation, has no more than its natural thick- 

 ness, 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. 

 Specimens of this kind may be rare, but a number have 

 come under the writer's observation, and in lungs, too, 

 that presented at other points of their substance the ex- 

 cessive interlobular exudation. 



Both of these forms show a tendency to confine them- 

 selves to particular lobules and groups of lobules of the 

 lung. They correspond, in short, to the distribution oi 



