MINUTE ANATOMY OF THE CAPILLARIES. 



285 



can be influenced in the most various modes by the con- 

 tractility of the cells. Everything, in fact, which favours or 

 checks their active motility influences their extravasation 

 (Hering), 



The finer capillaries consist only of a tube composed of cells 

 or of a cylindrical layer of protoplasm. As the capillaries 



. 52. 



Fig. 52. Capillaries from the hyaloid membrane of the Frog, a, 

 capillary wall ; 6, nucleus of th j same ; c, cells of the tunica adven- 

 tit:a ; d, processes of these cells clasping the capillary wall; e, stellate 

 c?lls anastomosing with the cells of the tunica adventitia. 



become larger, a delicate tunica adventitia is superadded, 

 which, in the hyaloid membrane of the frog (a membrane well 

 adapted for this investigation), is formed, according to the 



Y 2 



