PHYSICAL DIAGNOSIS OF THE LUNGS 125 



A dull, muffiod sound, which has been mentioned in the above classifi- 

 cation, is heard in the following conditions: In the tissues of the lung, 

 where the air cannot reach, as in hepatization; in croupous pneumonia; in 

 tuberculosis, provided that the diseased centre is not entirely surrounded 

 with tissue containing air; in tumors of the lungs; in hemorrhagic infarc- 

 tion; in sections of the lungs that are compressed by pleuritic or pericar- 

 dial effusions. (Edema of the lung is only accompanied with dulness 

 when it is well advanced. 



The dull sound is present, when an abnormal medium is between the 

 lungs and the pleximeter, as in the various pleural diseases; tumors of the 

 pleura; pleuritic or dropsical effusions; and also in certain pathological 

 alterations of the chest, as in oedema, or tumors. The more the tissues 

 fill up near the walls of the chest and the greater the density of the 

 medium between the pleximeter and the lungs, the more in- 

 distinct and muffled the sound becomes. 



The tympanitic sound is heard where there is any cavity 

 or hollow in the lungs, as in pneumothorax. In the alteration 

 of the tension of the parenchyma of the lungs, we find the 

 sound above pleuritic exudates and in the neighborhood of 

 large tumors of the lungs, or in compression of the lungs 

 from the pushing forward of the diaphragm due to tumors, or 

 ascites. It is also heard in moistening of the alveoli by fluids 

 and reduction of the contained air, as in the loose moist stage 

 of croupous pneumonia; and where there are many small tuber- 

 cular centres, in the tissue of the lungs, which are hollow in the 

 centre and contain air, and it is sometimes heard in oedema of 

 the lungs. Cutaneous emphysema of the walls of the chest ^^°- ^^•~* 



• • 1 mi Tn Stethoscope. 



gives a clear tympanitic sound. There are several modifica- 

 tions of this sound, such as the cracked-pot or metallic, tinkling percus- 

 sion sound, but these are not of much diagnostic value, as they appear 

 only when there may be large cavernous spaces in the walls of the 

 chest. 



Auscultation of the Lungs. — This is performed, either by putting the 

 ear directly against the walls of the chest, over the affected region (direct 

 auscultation), or by using a stethoscope (Fig. 59) (indirect auscultation). 

 (A form of stethoscope called the " membranate stethoscope," a modifica- 

 tion of the phonograph, has lately been introduced and used in the larger 

 animals with considerable success, but the person using it must be thor- 

 oughly familiar with the chest sounds and also with the instrument to 

 get the best results, but the writer finds that on account of its size it is not 

 of much practical use in the dog.) The first method is the best, especially 

 with restless animals. 



The ear distinguishes the true respiratory and accessory sounds. In 



