ACUTE CATAKRHAL BRONCHITIS. 477 



tubes are chiefly involved. This earher condition of the 

 membrane, resulting in arrest of natural secretion and conse- 

 quent dryness and rigidity of the tubes, is very shortly re- 

 placed by an increased secretion and consequent moistness and 

 relaxation. With the presence of liquid in the tubes, and its 

 varying conditions of quantity and viscidity, the sounds become 

 interrupted and modified by the passing of the air through 

 bubbles of mucus, and as these bubbles vary in size and 

 tenacity, so the sounds vary also. In the larger bronchi, where 

 the sonorous rhonchus was heard in the earlier stages, when 

 effusion exists the hard sound is modified to that of a mucous 

 bubbling or larger crepitation, so called ; in the smaller we 

 have the moist sibilant rale, or lesser crepitation. 



Occasionally the mucus may become so much inspissated 

 that, adhering at some particular point, the hardened material 

 seems to play to and fro by the action of the air passing along 

 the tube, somewhat in the manner of a valve, thus yielding a 

 sharp clicking noise. It is to the relative amount and distri- 

 bution of these sounds, and to the amount of fluid in the 

 tubes, that we have to attend in arriving at an opinion as to 

 the severity of the attack and the dangers to be apprehended. 

 When the deeper and more sonorous sounds, dry or moist, are 

 in excess of the higher-pitched sibilant rales, there is less 

 danger to be feared than in opposite conditions. In such the 

 disease is chiefly confined to the larger bronchi, while the 

 more extensively distributed and finer tubes are comparatively 

 free. When the smaller bronchi are specially the seat of in- 

 flammation, the relative disproportion between the inspirations 

 and expirations becomes more marked ; the latter being much 

 prolonged, and the danger in all commensurately increased. 



Percussion, when exercised over the region affected, yields 

 no positive evidence of disease, unless over such portions of 

 the lung-structure as from auscultation we find, from the 

 absence of the healthy murmur, to be wanting in functional 

 activity. These portions, from the still existing resonance, we 

 find to contain a certain quantity of air ; this condition we judge 

 to owe its existence to the obliteration of one or more bronchi of 

 which we have already spoken, and tending to collapse of lung- 

 tissue consolidation, atrophy, and pulmonary emphysema. 



The usually accompanying cough, dry and sonorous at first. 



