AUSCULTATION. 527 



side of its walls to that opposite, as a result of sounds trans- 

 mitted from the deeper-seated parts. The first-mentioned 

 cause is undoubtedly the most common, and is commonly 

 best heard after the animal's position has been changed. Thus, 

 when the patient is lying, the collapsed lung, or it may be 

 shreds of false membrane, become bathed in the liquid, which 

 is not plentiful enough to reach these parts when standing. 

 On changing the former for the latter position, accordingly, 

 a number of drops fall from above into the liquid below, and 

 they will be found to succeed each other with a gradually 

 decreasing rapidity until they finally cease altogether. 



A friction sound is developed by the pleurae as a result of 

 the deposition of lymph on those first attacked by inflamma- 

 tion. It consists in superficial, quick, jerking sounds, com- 

 parable to that heard on applying the palm of the left hand 

 over the right ear, and rubbing its back softly with a finger 

 of the right. Few jerks are heard at each respiratory act, 

 and chiefly or exclusively at the lower part of the thorax, 

 where the contained organs enjoy the greatest freedom. The 

 sounds are most marked during inspiration, though they may 

 likewise be produced during the respiratory act, or during 

 the beats of the heart from the movement caused by the con- 

 traction of that organ. They are especially distinct in the 

 cow and dog, from the thinness of the muscles on each side 

 of the sternum. After the lapse of twelve, twenty-four, or 

 thirty-six hours, the sounds usually disappear, on account of 

 pleural effusion; during recovery, when the effused liquid 

 has been taken up, friction is again heard until the exuded 

 lymph has been absorbed. It is accompanied by vibrations 

 of the thoracic walls, perceptible to the touch. 



Closely allied to the friction sound is a creaking noise, 

 developed by movement in a layer of coagulated lymph, by 

 which the costal is bound to the pulmonic pleurae. 



