DIGESTIVE SECRETIONS AND THEIR CONTROL 433 



FIG. 137. Forms of glands. A, a simple secreting surface; a, its epithelium; 

 b, basement membrane; c, capillaries; B, a simple tubular gland; C, a secreting 

 surface increased by protrusions; E, a simple racemose gland; D and G, com- 

 pound tubular glands; F, a compound racemose gland. In all but A, B, a"nd C 

 the capillaries are omitted for the sake of clearness. H, half of a highly developed 

 racemose gland; c, its main duct. 



