100 liiU'i-stilial Einpliysoiua ui' the Luiij,^s. 



lead to rupture of tlie alveolar walls. The advent of the con- 

 dition is therefore observed frequently after convulsive and 

 forced attacks of cough. The following diseases may be in- 

 direct causes of the ati'ection: acute catarrh and croupous in- 

 flammation of the liner bronchi; foreign bodies accidentally 

 entering the air passages; improper drenching; pointed 

 bodies which may directly injure the alveolar walls ; over- 

 exertion of the abdomiiuil press in pulling a heavy load, 

 in delivery, in vomiting or in efforts of animals which liave 

 met with an accident. Rupture of the alveoli may also be 

 brought a])0ut by continuous bellowing, by forced expiration, 

 in rapid running, in excitement, in railroad transportation, in 

 falling or kicking (Arendt saw a case of this kind in a horse), 

 after traumatic insults to the chest, etc. If the resisting power 

 of the pulmonary tissue has been lessened, these forces may 

 more easily lead to a solution of continuity, hence interstitial 

 emphysema is often seen following alveolar emphysema. 



According to Michels, Detmers and others, interstitial eniphysenia 

 of the lungs occurs to an epizootic extent in some marshy parts of Hol- 

 land and Belgium among cattle (pneumatosis l)0vum). The cause of the 

 disease has not yet been ascertained definitely, but it appears to stand m 

 causal relation with frequent bronchial catarrhs due to exposure to cold. 

 (Joest thinks that these cases are interstitial emphysema due to lung 

 strongylosis of cattle, see page 72). 



Anatomical Changes. Air bubbles varying in size from a 

 nut to a fist, exceptionally also as large as a child's head, are 

 found beneath the pleura and in the pulmonary parenchjana; 

 the smaller bubbles are often present in large numbers and 

 densely crowded. Otherwise the pulmonary tissue may be 

 healthy or it may show the changes of a prhnary basic disease. 

 The connective tissue of the mediastinum, of the chest aperture, 

 of the neck and the sul)peritoneal tissue, may occasionally like- 

 wise contain air bubbles. 



Symptoms. The air which has entered into the interstitial 

 connective tissue soon compresses the neighboring alveoli; 

 hence the respiratory surface becomes correspondingly dimin- 

 ished. In some eases the disease therefore sets in suddenly 

 with dyspnea which progresses so rapidly that the animals 

 sometimes are cyanotic and threatened by suffocation after a 

 few hours. The percussion sound either remains normal or 

 is accompanied l)y t>nnpanitic accessory sounds. In the presence 

 of large subpleural air bubbles it may be purely tjiiipanitic. 

 The respiratory sounds, both in expiration and in inspiration, 

 are occasionally accompanied ])y crepitant and cracking noises. 

 In some cases, particularly in cattle, subcutaneous emphysema 

 is developed subsequently and moderate pressure on the tense, 

 but otherwise healthy, skin elicits crepitation; the percussion 

 sound is in these places tjmipanitic. The subcutaneous em- 



