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arches, passing between the main artery and vein, and are produced by 

 the junction of prolongations, sent from both the artery and vein, with 

 certain elongated or star-shaped cells, in the substance of the tail. When 

 these arches are formed and are permeable to blood, new prolongations 

 pass from them, join other radiated cells, and thus form secondary arches 



FIG. 434. 



FIG. 434. Development of capillaries in the regenerating tail of a tadpole 

 cords of protoplasm. (Arnold.) 



FIG. 435. The same region after the lapse of 24 hours, 

 have become channeled out into capillaries. (Arnold.) 



FIG. 435. 



a, 6, c, d, sprouts and 

 The "sprouts and cords of protoplasm" 



(Fig. 434). In this manner, the capillary network extends in proportion 

 as the tail increases in length and breadth, and it, at the same time, be- 

 comes more dense by the formation, according to the same plan, of fresh 

 vessels within its meshes. The prolongations by which the vessels com- 

 municate with the star-shaped cells, consist at first of narrow pointed 



FIG. 436 Capillaries from the vitreous humor of a foetal calf. Two vessels are seen connected 

 by a cord of protoplasm, and clothed with an adventitia, containing numerous nuclei, a, insertion 

 of this "cord" into the primary walls of the vessels. (Frey.) 



projections from the side of the vessels, which gradually elongate until 

 they come in contact with the radiated processes of the cells. The thick- 

 ness of such a prolongation often does not exceed that of a fibril of fibrous 



