574 BKONCHITIS. 



Dr Gairdner has shown, in the human subject, that from 

 obstruction of the bronchi by mucus of a certain degree of 

 tenacity, the air-cells of portions of lung collapse so as to 

 cause them to sink in water and assume the appearance of 

 foetal lung. Dr Gairdner* says : 



" Bronchitic collapse of the lung occurs under two distinct aspects 

 the diffused form, and the limited or lobular form. Of these, the 

 latter variety is the more striking and characteristic, and has been, 

 especially in the lungs of children, the subject of more discussion than 

 the former; but the diffused form is by far the more common, and is 

 in fact of very frequent occurrence, at least in its slighter degree,? 

 Both forms present the same fundamental changes of the pulmonary 

 tissue, which is usually of a dark violet colour externally, as seen be- 

 neath the pleura, and internally of a more or less deep brownish-red, 

 or mahogany tint. The colour, however, is by no means an invariable 

 criterion, depending almost entirely on the amount of blood in the col- 

 lapsed tissue. The affected parts are always more or less condensed; 

 this condensation may amount to a mere diminution of the crepitation, 

 or to a total absence of it, in which case portions are usually found to 

 sink readily in water. These latter portions are both more flaccid and 

 much less friable than the pulmonary tissue when in a state of red he- 

 patization, and they differ greatly from this lesion in the aspect of their 

 section and the nature of the fluid it yields to the knife. In every 

 variety of true pneumonic consolidation in which the lung is completely 

 void of air, the air-cells are occupied by a deposit, presenting to the 

 naked eye (and still more distinctly to a power of 20 or 30 diameters) 

 the well-known granular aspect of the hepatized lung. If the deposit 

 is fluid, or semi-fluid, it is capable of being pressed out, or scraped off, 

 in the form of a thick opaque emulsion-like matter, of yellowish, orange, 

 or grey colour, and in all cases it shows under the microscope abundant 

 granular elements and cell-structures of the kinds usually found in in- 

 flammatory exudations in parenchymatous organs. In the collapsed 

 lung, on the contrary, the section is comparatively smooth, having the 

 appearance, as described by Lsennec, of muscular flesh; it presents no 

 trace of granulations, and yields, on pressure, or to the knife, only a 

 semi-transparent bloody serosity, which, under the microscope, is seen 



* On the Pathological Anatomy of Bronchitis, &c. IS 50. 



