SYSTEMATIC SYNTHESIS OF TISSUES INTO ORGANS. 317 



887. Remark. THE ARRANGEMENT OF THE CAPILLA- FIG. 205. 

 KIES is so exactly in accordance with the structure to 

 which they belong that an examination of a small por- 

 tion of a capillary network would determine whence it 

 came. In Fig. 205, 5, 5, represents a network of capil- 

 laries around the root of a hair, 3. 



888. THE CAPILLARIES ARE CONSTRUCT- 

 ED of a homogeneous membrane, like base- 

 ment membrane, with nuclear spots in its 

 sides, shown in c, Fig. 206, capillaries, into 

 which a, an artery, opens. 



889. THE CAPILLARIES OPEN from the 

 arteries on the one hand and into veins on 



the other, as a rule, but there are ex- FI G- 206. 



ceptions, 1st, in which capillaries only- 

 are the means necessary for a very 

 limited circulation, and, 2d, where ca- 

 pillaries open from and into veins, 

 for example in the liver. 



890. THE USE OF THE CAPILLA- 

 RIES is to bring the Blood into very 

 near relations with the parts upon 



which it is to act, or with the substances that are to 

 act upon it. 



891. There DO NOT APPEAR to be any apertures or 

 pores IN THE SIDES OF A CAPILLARY more than there are 

 in the sides of a soap-bubble, but the substances it con- 

 tains pass through it at any point, and substances pass 

 into it without any rupture. Where one occurs, as in 

 Fig. 204, the entire contents burst out. 



892. THE SUBSTANCES ABOUT TO PASS OUT FROM THE 

 CAPILLARY approach its inner surface from the current 

 that is more quickly flowing through its centre, then hesi- 

 tate, are quiet for an instant, and, in the twinkling of an 

 eye, appear on the outside. 



887. What said of ? 888. How are ? 

 891. What ? 892. What said of ? 



J. How do - ? 890. What is f 



