CONSUMPTION OF THE LUNGS. 223 



other forms of solidification of the parenchyma, which, when cut into, 

 nearly always exhibit small points which suggest the idea of miliary 

 tubercles. 



It is only in rare cases that the diffuse consolidation of the lung- 

 substance presents the granular aspect and other characteristics of a 

 lung hepatized by croupous pneumonia. Far more commonly, there is 

 that homogeneous, dull-looking infiltration with smooth section, which 

 we have described as the product of acute and especially of chronic 

 catarrhal pneumonia. As a rule, the gelatinous infiltration has already 

 undergone the transformation peculiar to cheesy degeneration of 

 inflammatory products. If the latter have but recently commenced, 

 we see, upon the gray or grayish-red dead lustre of the cut surface, a 

 few yellow, lustreless marblings. If the caseous metamorphosis be 

 further advanced, the yellow places are larger, until at last the entire 

 solidified portion of the lung is converted into a yellow, cheesy mass. 

 After the infiltration has become caseous, it may undergo immediate 

 liquefaction, and, together with the tissues, break down into a creamy 

 puruloid matter. Thus cavities filled with the so-called tubercular pus 

 are formed. At last a communication is set up with a neighboring 

 bronchus, through which its contents are discharged by coughing. 

 The walls of these cavities are irregular and interrupted ; the pul- 

 monary parenchyma about them is infiltrated with caseous matter, and 

 is in a more or less advanced state of disintegration. 



The gelatinous or catarrhal infiltration, which, when attacked by 

 cheesy metamorphosis, and softening of the infiltrated lung-substance, 

 leads to the formation of these cavities, is at first generally confined to 

 single lobules. If the diseased lobule be situated near the surface, 

 the solidified spots bear the peculiar wedge-shape of the peripheral 

 lobules. When seated more deeply within the lung, they form rounded 

 indurations, or, where the process is restricted to the immediate vicin- 

 ity of separate bronchi, the consolidation runs along the course of the 

 tube. By repetition of the process, and by confluence of many of the 

 lobular centres, a whole lobe or even an entire lung may be solidified 

 and become the seat of vast destruction. 



But caseous infiltration of the pulmonary tissues, from whatever 

 form of pneumonia it may proceed, does not in all, nor even in the 

 majority of cases, result in immediate disintegration of the seat of the 

 cheesy infiltration, and in formation of a cavity. Such an event only 

 takes place under peculiar circumstances, and perhaps when the dis- 

 order is of extreme severity. It is probably brought about through 

 the crowding together of the accumulated cells in the air-vesicles, 

 whereby they not only encroach one upon another, but exert a pres- 

 sure upon the surrounding tissues and their vessels, thus depriving the 



