THE BLOOD-VESSELS. 



149 



spection of capillary reticula will generally enable us to decide 

 the nature of the tissue or organ in question. From a physio- 

 logical point of view, we recognize a causal relation between 

 high capillary development and great functional activity. 

 Therefore, the abundance of capillaries will determine the 

 physiological importance of an organ. 



The chief forms of ramification may be grouped as follows : 

 1. Loops (a), simple or compound; e.g., the skin and the hard 



FIG. 62. Capillaries from the hyaloid membrane of the frog: er,o, capillary-wall; 6,6, nuclei of the 

 same; c,c, cells of the tunica ad ventitia ; rf,rf, processes of these cells clasping the capillary-wall; e, stel- 

 late cell anastomosing with the cells of the tunica adventitia. Eberth. 



palate ; (b) reticulated (the intestinal villi). 2. Tufts (the kid- 

 ney). 3. Irregularly polygonal networks (the glands and the 

 mucous membranes). 4. Rounded reticula, with round or 

 polygonal meshes (adipose tissue). 5. Reticula with elongated 

 meshes (the muscles, bones, and tendons). There would be a 

 certain satisfaction in knowing that this or that vessel had a 

 precise breadth, and its coat a certain thickness. The precision 

 would be apparent, however, rather than real, because such 



