Auscultation. 



193 



anaemia, in low fevers, in all very prostrate conditions from the 

 mere want of power to dilate the chest ; in general emphysema 

 (broken wind, heaves), in general miliary tubercular deposit in 

 the lungs, or in that form in cattle in which the tubercle has been 

 replaced by cretaceous deposits, from the animal's inability to 

 fully dilate the air cells ; in enteritis, peritonitis and metritis 

 the chest is less fully dilated because of the pain attendant on 

 that act, and the breathing being short and quick the murmur is 

 correspondingly low. In certain brain diseases with sluggish 

 respiration the sound is equally feeble. 



Partial diminution of murmur is more .surely indicative of 

 lung disease. It may arise from partial congestion when a sup- 

 plementary murmur will be observable over other parts of the 

 lungs, and a crepitant rSle soon appears in the congested part ; 

 from local emphysema in which there is increased resonance in 

 percussing the part ; from tubercular or cretaceous deposit, when 

 there will be exaggerated murmur elsewhere ; or from bronchitis 

 with blocking up of one or more small bronchial tubes and with 

 louder respiratory sound in other parts. 



Absence of respiratory murmur may be due to various 

 causes, all of a diseased nature. Hepatisation of lung may be 

 recognized when this condition is found associated with a crepi- 

 tating rale around the margin of the silent part, and when per- 

 cussion shows its solidity and want of resonance. Splenisation 

 is associated with absence of respiratory sound and dullness on 

 percussion, but no surrounding crepitation. Absence of sound 

 in water in the chest is confined to the lower part of the chest, 

 keeps the same level and ratio of increase in front and behind, 

 and in the horse on the two sides, and has been preceded by the 

 characteristic catching breathing and the friction sounds of 

 pleurisy. Large tumors and extensive and circumscribed tuber- 

 cular deposit will give rise to absence of sound over a limited area, 

 and plugging up of one or more bronchial tubes will lead to a 

 similar result. Hepatisation of lung and water in the chest are, 

 however, the common causes of loss of respiratory murmur. 



The bronchial or tubal sound may be increased in pitch and 

 in harshness in two conditions, ist. In the early stages of bron- 

 chitis when the lining mucous membrane of the air passages is 

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