Anatomical Changes. Symptoms. 155 



the lungs appear uniformly grayisli-wliite or yellowisli-gray 

 and lardaceous. They contain little air and are, consequently, 

 firm. The lower and inferior portions usually show only a few 

 nodules and are otherwise similar. Microscopically, we find 

 proliferation of alveolar epithelia, much new formation of con- 

 nective tissue, compression of the alveoli ; the histologic picture 

 has some similarity to that of carcinoma. There is, on the 

 other hand, some similarity between lardaceous pneumonia of 

 horses and multiple adenoma of sheep (see tumors of the 

 lungs), and also between focal chronic pneumonia following 

 bronchitis scleroticans of the horse. However, in this form 

 of chronic pneumonia, inflammatory new formation of tissue is 

 found, particularly in the peribronchial tissue, along the blood 

 vessels and in the interalveolar tissue (l)ronchopneunionia 

 fibroplastica, Griiter). In this latter disease lardaceous-look- 

 ing foci are also generally seen which, however, grow at most 

 up to the size of a fist. 



In pneumoconiosis one sees in the lungs either fibrous- 

 calcareous nodules or streaky cicatricial l)ands, or on the con- 

 trary, the picture of a fibrous bronchopneumonia ; after coal- 

 dust inhalation slate-black spots are also oliserved. The ana- 

 tomical picture usually includes the signs of chronic bronchial 

 catarrh and chronic pleurisy. 



Symptoms. The respiratory surface of the lungs becomes 

 diminished and the expansion on inspiration is impeded in 

 consequence of the new formation and subsequent contraction 

 of the connective tissue. Hence, difficult resx)iration is noted 

 in cases of a somewhat more extensive affection; it is partic- 

 ularly noticeable during work and leads to rapid tiring out of 

 the animal. The signs of chronic In-onchial catarrh are also 

 usually present, such as a dull, weak cough, scanty, usually 

 sharp (dry) rales, or purring or whistling sounds, etc. They 

 are often noticeable only after deep inspiration, after exercise, 

 after coughing, or after one has previously closed the nostrils 

 of the animal. Disturl)ances of nutrition l)ecome marked 

 later on. 



On careful percussion, particularly on corresponding places 

 of the two sides of the thorax, one can usually make out a more 

 or less distinct dullness, occasionally tympanitic sounds over 

 the anterior and inferior portion, as a rule behind or below the 

 scapula. The vesicular breathing is weakened in the area of 

 dullness or is entirely alisent ; in other cases one may have, on 

 the contrary, bronchial breathing, or intensified, drawn respira- 

 tory sounds. In extensive shrinking of the pulmonary tissue 

 many pulmonary capillaries become obliterated; consequently 

 the second pulmonary sound is intensified. 



The disease runs its course without fever, and this is im- 

 portant as a point of differential diagnosis with reference to 

 acute pulmonary consolidation. However, bronchial catarrh, 



