104 HYPERTROPHY, HYPERPLASIA, METAPLASIA, REGENERATION. 



new connective-tissue cells concerned in the formation of fibrillar stroma 

 are called fibroblasts ( Fig. 34 ) . As the fibrous stroma increases in amount 

 the cells, at first relatively abundant, become elongated and flattened, 

 until as the new tissue approaches maturity the more or less dense 

 fibrillar stroma preponderates, pressing the cells between its bundles 

 or layers into variously shaped plaques, often fusiform or linear in 

 profile. 



In the formation of fibrillar connective tissue from eudotheliuin the 

 endothelial cells of thin-walled blood-vessels increase in size, stretch 

 slender bud-like extensions into the adjacent tissue, where, after mitotic 

 division, they assume a role altogether identical with that of the ordinary 

 connective-tissue cell. 



The formation of new connective-tissue cells may be large or it may 

 be limited to the production of a single pair of cells ; the stroma may be 

 scanty or abundant, loose or dense ; the process is essentially the same, 

 namely, the division of cells by mitosis, and the formation by them, or 

 under their influence, of more or less fibrillar stroma. This process, it 

 will be seen, is practically identical with the formation of fibrous tissue 

 in the embryo. 



But here, as elsewhere, the character and extent of new tissue pro- 

 duction are largely influenced by the environment, and particularly by 

 the nutritive supply, so that the formation of new connective tissue in 

 any considerable amount is closely linked to the development of blood- 

 vessels. 



The Formation of Blood-Vessels. The formation of blood-vessels in 

 post-embryonic life is believed always to start in a budding or sprouting 



FIG. 35. DEVELOPING BLOOD-VESSELS ix NEW-FORMED TISSUE. 



of the endothelial cells of pre-existing capillaries. The sprouts, directed 

 outward from the eudothelia of the capillaries, consist at first of slender, 

 conical, or filiform projections of cytoplasmic substance (Fig. 35). Now 

 the cytoplasm of the cell from which the sprout springs may increase in 

 amount and its nuclei divide by mitosis, so that the base of the sprout 

 may consist of a multinuclear mass of cytoplasm or of a cluster of new- 



