Diseases of the Mediastinum. 389 



gullet in ill-advised interference in cases of thoracic choking, or 

 again in acute inflammations of the lungs (lung plague, con- 

 tagious pneumonia, inhalation broncho- pneumonia), or in 

 pleurisy. The more tardy cases are likely to follow on neo- 

 plasms, tuberculosis, hydatids (echinococcus, cysticercus ten- 

 uicoUis) or actinomycosis. 



In sheep, in addition to choking, pulmonary inflammation 

 and tuberculosis, there are parasitisms (lung worms, hydatids, 

 linguatula) and infectious caseous adenitis. 



In dogs the affection may attend on distemper, infectious 

 bronchitis, ossifying enchondroma (Nocard), and other neo- 

 plasms, simple and malignant. 



In dogs, cats and pigs lacerations and other injuries of 

 of the gullet with sharp-pointed bones become a cause of medias- 

 tinal inflammation, especially adenitis. 



Symptoms. In acute cases supervening on other inflammatory 

 diseases of the chest the symptoms are masked by the previous 

 and persisting signs of surrounding disease, and as objective 

 physical signs are obscure in the larger quadrupeds, the case is 

 not discovered until the necropsy. When not covered up by 

 such concurrent symptoms, there is usually marked dyspnoea, 

 tenderness perhaps on percussion on the median line of the 

 sternum, diflBculty in swallowing, in cattle absence of eructation 

 and the supervention of gastric tympany, in dogs and pigs nausea 

 and vomiting, and in some cases paresis of the larynx and stertor. 



When the connective tissue is thickened, organized and press- 

 ing on the tissues, another class of symptoms may be added : 

 There is tense dilatation of the jugulars persisting even during 

 inspiration, the result of obstruction of the blood-flow in the an- 

 terior cava ; there may be oedema of the lips, nostrils and eyelids, 

 dark red congestion of the conjunctiva and nasal mucosa, and 

 fulness of the cervical and facial veins. The dropsy may 

 extend to the fore limbs and even to the hind. In the human 

 subject the suppression of the pulsation during inspiration to re- 

 appear with expiration is a marked feature. There may follow 

 hepatic congestion, dropsy and ascites. In such a case the veins 

 of the trunk, hind limbs, and fore are prominently dilated, as well 

 as those of the neck and head. The heart sounds are dull and 

 muffled owing to the compression of the base of the heart and 

 the interference with its systole. 



