Formation of Blood Vessels. 241 



being widened by blood pressure and growth of the wall (increase 

 of surface by multiplication of the parietal endothelial cells) ; 

 smooth muscle grow-ing from the existing arteries into the newly 

 formed vessels, and the surrounding fibroplastic tissue aiding in the 

 formation of elastic fibres. (Regeneration of blood vessels has 

 been especially studied by J. Arnold, Jos. ]\Ieyer, Billroth, C. Weil 

 and Thoma.) 



The development of angio-fibroplastic tissue is accompanied by 

 more or less manifest phenomena of inflammation (hyperemia, 

 exudation of leucocytes) and is therefore in a sense a result of pro- 

 ductive inflammation. Depending upon the number of blood ves- 

 sels present and the relative amount of proliferated connective tissue 

 the new structure presents a reddish-gray, grayish-white or pure 

 white, swollen appearance, semitransparent and of a shape conform- 

 ing to that of the lesion which it has followed. \Mien it develops 

 diffusely, as in parenchymatous organs, to replace destroyed gland- 

 ular tissue, it gives rise to more or less marked induration of the 

 part (indurative inflammation), or forms translucent hard thicken- 

 ings (in fasciae, serous membranes), bands of adhesion (adhesive 

 inflammation) and sometimes villus-like fringes. In focal devel- 

 opment it forms white trabecular or nodular connective tissue 

 masses (in infarcts of the kidney) ; as the result of a demarcating 

 inflammation about some blood clot or foreign body it constitutes 

 a connective tissue capsule. On the free surfaces of wounds the 

 new formation is seen as a finely granular soft tissue, producing an 

 exudate, with a deep red or reddish gray color from the abundance 

 of capillary buds in its structure : it is known as gramilation-tissue. 



All fibro-angioplastic tissue is at first likely to form a greater 

 bulk than the lesion which it replaces. There exists an excessive 

 production of the young cells and these cause an excess of inter- 

 cellular material. \\'ith restoration of normal tissue tension and 

 maturation of the growing tissue, these originally enlarged cells 

 shrink and the intercellular substance decreases ; the fibrils are ar- 

 ranged in a parallel fashion from the tension and pressure of the 

 neighboring structures influencing them; some of the capillaries 

 become obliterated, that is, narrowed, from pressure by the shrink- 

 ing fibroplastic tissue. In this way, too, the whole tissue, some- 

 times, because elastic tissue is produced in deficient amount or not 

 at all, becomes dense and hard and is changed into cicatricial tissue. 

 This is apt to contract still further, thus forming in the surface of 

 the skin and organs depressions or indentations of radiating stellate 

 form. 



