110 DISEASES OF THE RESPIRATORY ORGANS. 



of the lung where the air cannot reach, as in hepatization; in 

 croupal pneumonia; in tuberculosis, provided that the diseased 

 centre is not entirely surrounded with tissue containing air ; in 

 tumors of the lungs; in hemorrhagic infarction; in sections of 

 the lungs that are compressed by pleuritic or pericardial effusions. 

 CEdema 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 cedema, 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 indistinct 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 iind it above pleu- 

 ritic exudates and in the neighborhood of large tumors of the 

 lungs, or in compression of the lungs from the pushing for- 

 ward of the diaphragm due to tumors, ascites ; also moistening 

 of the alveola by fluids and reduction in the contained air, as 

 in the loose moist stage of croupal pneumonia ; also where there 

 are many small tubercular centres in the tissue of the 



Fig. 35. -^ . 



lungs, which are hollow in the centre and contain air, 

 and sometimes in cedema of the lungs. Cutaneous 

 emphysema of the walls of the chest gives a clear 

 tympanitic sound. There are several modifications 

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

 percussion-sound ; but these are not of much diagnos- 

 tic value, as they appear only when there may be 

 large cavernous spaces in the walls of the chest. 



Auscultation of the Thorax. 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. 35) (indirect ausculta- 

 tion). A form of stethoscope called the " Phonendo- 

 stethosoope. scope," a modification of the phonograph, has lately 

 been introduced and used in the larger animals with considerable 

 success, but the translator finds that on account of its size it is 



