86 PRACTICE OF MEDICINE. 



when well marked, is a very characteristic sign. A change of posi- 

 tion will also alter this line in a manner quite distinctive, and, what 

 can happen only in liquid effusion, — the dull sound always accom- 

 panies the liquid as it gravitates to the lowest parts. When the 

 effusion is copious, the entire side, from the clavicle down, may be 

 dull. M. Reynaud has pointed out another effect of effusion, which 

 may furnish a diagnostic sign, in its intercepting the slight fremitus 

 or vibration which accompanies the voice in all parts of the chest. 

 The hand applied to a healthy chest readily feels this general 

 vibration ; but a layer of liquid, interposed between the lung and 

 the chest, acts as a damper, and prevents the transmission of the 

 vibration. 



The respiration is usually heard becoming bronchial^ as the effu- 

 sion increases up to a certain point ; but then, as the bronchi them- 

 selves become pressed by further increase, it becomes faint, and at 

 last ceases. 



The voice furnishes a valuable sign. If it traverses a thin layer 

 of liquid interposed between the lung and the ribs, it throws it into 

 vibrations, and is itself modified, and rendered sharp and tremulous, 

 resembling the bleating of a goat or lamb. This modification of 

 the voice M. Laennec therefore called cBgophony. Its most dis- 

 tinctive mark is its tremulous or subsultory character. This is re- 

 garded as a pathognomonic sign of effusion into the pleura, as it 

 can only be produced by this cause. 



When the effusion is very considerable from the commencement, 

 or becomes so during the progress of the disease, the segophony dis- 

 appears, and the respiration is no longer heard, unless where old 

 adhesions retain some part of the lung near the ribs, and prevent it 

 from being forced back by the effusion. The intercostal spaces (j|p- 

 come enlarged and elevated ; the affected side is more expanded than 

 the sound one, but is no longer influenced by respiration, its immo- 

 bility forming a strikins; contrast with the great mobility of the other, 

 in which the respiratory murmur is increased in intensity, so much 

 so as to assume the " puerile" character. Now, as the sound of this 

 respiration is sometimes heard on the diseased side, through the 

 liquid, it will be necessary to guard against the error of mistaking 

 it for a faint respiration on that side. 



Another effect of a large collection of liquid in the chest is to dis- 

 place the viscera in a remarkable manner. Thus an effusion on the 

 left side will often displace the heart, and make it pulsate under, or 

 even on the right of, the. sternum. The liver will be pushed down- 

 wards by a large collection of fluid on the right side. These signs 

 are important, because they distinguish this disease from hepatiza- 

 tion of the lung, which is liable to be mistaken for pleuritic effusion, 

 but which produces no such displacements. A useful criterion of 

 this kind, drawn from percussion on the sternum, has been pointed 



