240 



Regeneration. 



generation of connective tissue are not fully formulated ; their forma- 

 tion is, however, a slow process. It is only after four or six weeks 

 or after several months after repair by the fibroplastic tissue that 

 elastic fibrils appear in the intercellular substance; and even after 

 years these do not attain the diameter of the original elastic ele- 

 ments. 



Connective tissue, modified to form adipose tissue by fatty infiltra- 

 tion, is capable of proliferation to the same extent as ordinary connective 

 tissue cells. The nucleated protoplasmic remnant of the fat cell undergoes 

 division, and the new cells usually at first accumulate in the fat vacuole 

 within the old cell membrane. 



Formation of blood z'csscls takes place by a process of budding 

 and division of the endothelial cells from the existing capillaries. 

 The protoplasm of the endothelial cells in the walls of the old ca- 

 pillaries which have remained intact send out pointed, conical proc- 

 esses, which lengthen out in thread like manner, and penetrate 



■■-g^S*'*^' 



•;U3^jg^< 



Fig. 44. 



Vascular sprouts, highly magnitied : (after 'i'homa). The long thread-like ends 

 of the sprouts are only partly reproduced. 



between the proliferating fibroblasts. Coincidently mitosis of these 

 endothelial cells takes place and at the base of the bud cellular 

 division begins and the endothelial cells (angioplasts) proliferate. 

 These new elements lie alongside of each other and fuse, with their 

 often curved and reticular branches, into solid cords of cells. 

 From these the capillary tubes are produced by the forcible pene- 

 tration of the blood from the old vessel in between the dividing 

 endothelial elements, thus making a space filled with blood. This 

 proceeding at all places where these buds are forming, gradually 

 the whole network becomes canalized. From some of the capillaries 

 arteries are formed, from others veins, the lumen of the tubes 



