STRUCTURAL CHANGES DUE TO DAMAGE. 



307 



in the nutrition of the tissue. There is a manifest advantage to 

 the whole organism in this absence of lymphatics in granulation- 

 tissue, for the absorption of injurious substances from the region 

 beyond the granulations is hindered. But the nutrition of the 

 granulations themselves is impoverished and the fibrous tissue 



FIG. 272. 





Newly formed fibrous tissue from a case of pleurisy : a, pulmonary alveolus filled with an 

 exudate largely composed of leucocytes (pneumonia ; stage of gray hepatization passing 

 into resolution) ; b, alveolus, from which the disintegrated exudate has fallen out. 

 Before the alterations in structure due to inflammation took place this alveolus, and 

 the one above it, lay immediately beneath the pleura. The thin pleuritic membrane 

 has now been destroyed and its place taken by the fibrous tissue of inflammatory pro- 

 duction, which fills nearly the whole field of vision, c, thin-walled bloodvessel in that 

 fibrous tissue. This and those like it form a part of the older portion of the granulation- 

 tissue which has replaced the fibrinous exudate at first covering the lung (see p. 313). The 

 granulation-tissue between these vessels has organized into a young fibrous tissue, d, 

 younger granulation-tissue; e, recently formed bloodvessel in the latter;/, masses of 

 carbon deposited in the tissues by leucocytes, which have transported it thither from the 

 air-passages. These deposits existed before the acute inflammation began. This form 

 of pigmentation is called "anthracosis." 



that results from its differentiation is of comparatively low vital- 

 ity. While the tissue is young, succulent, and highly vaseular- 

 ized by capillaries, this deficiency in its organization may not be 

 apparent ; but as the intercellular substances contract they com- 

 press the vessels and cause obliteration of many of them, with 

 atrophy and disappearance of their cellular walls (Fig. 273). 



