316 



DETAILED SYNTHESIS. 



Capillaries. 



886. CAPILLARIES are exceedingly minute tubes dif- 

 fering slightly in size in different parts, but uniform in 

 size in a given part, united with each other so as to form 

 a network, the meshes of which vary in size and arrange- 

 ment in different parts, according to their structure and 

 requirements in respect to Blood. The capillaries are 

 the most essential parts of the circulation, always exist- 

 ing first and acting last in life, the other parts being 

 added in order to pass the blood from one set of capil- 

 laries to another. 



FIG. 204=. 



Fig. 204 represents a portion of frog's foot, during life, very much mag- 

 nified : a, an artery ; b, a vein deeper than c, a network of capillaries near 

 the surface. In the network the two kinds of blood-cells are noticeable; 

 the red ones are largest, and, from compression in the minute capillaries, 

 somewhat elongated. The white cells are also noticeable at 1, in the arte- 

 ry, near its walls, the red cells pouring along in the centre so rapidly as 

 not to be separately discerned, and only as a dark current, as represented. 

 Above c, in the centre, a capillary has been ruptured and cells are crowd- 

 ing into the adjoining mesh. The irritation thus caused has retarded the 

 circulation in the neighboring capillaries, and the cells are crowding each 

 other. The irregular black spots are pigment-cells that give color to the 

 part. 



686. What are ? What different figures represent capillaries? Describe 

 Fig. 204. 



