526 AUSCULTATION. 



soon gives place to the ordinary respiratory murmur. In 

 some cases, with a coarser variety of the crepitant rale, the 

 sound is heard to some extent in expiration, probably from 

 its being developed in the small bronchial tubes as well as in 

 the air-cells. All pneumonias are not accompanied by a 

 crepitant rale ; in weak animals with an adynamic type of in- 

 flammation, tending to gangrene, and in cases of croupous 

 pneumonia in cattle, in which fibrinous exudations exist in 

 the ultimate bronchia and air-cells, this sound may be either 

 absent, or so weak as to be all but inaudible, even to a well- 

 practised ear. Even when it is heard it may owe its existence 

 to other causes, such as pulmonary cedema, capillary haemor- 

 rhage, or any other means whereby liquid becomes effused 

 into the ultimate bronchial tubes or air-sacs. 



The subcrepitant is an exaggeration of the crepitant rale. 

 It holds an intermediate place between the latter and the 

 mucous rale, and is comparable to a moderate effervescence in 

 beer or other liquid. It has a bubbling character like the 

 mucous, but the bubbles seem to be much smaller, and the 

 sound is much finer. This rale may be taken to indicate 

 existing broncho-pneumonia, with some exhalation of blood 

 into the tubes. It is the spumous rale of Leblanc. 



Metallic tinkling is another peculiar superadded sound. 

 It may be imitated by striking a pin gently against a glass 

 vessel, or by applying the palm of the hand closely over the 

 ear, and giving it a smart tap on the back with the median 

 finger of the right. As a rule this sound is only produced 

 when air and fluid co-exist in a closed cavity, as in that of the 

 pleura, or in an excavation in the lungs. It may result from 

 a drop falling from the roof of the cavity into the liquid 

 beneath ; it may likewise depend on the ascent of a bubble 

 of air through the liquid, and its bursting on the surface, or 

 on the sudden reflection of the air in the cavity from one 



