472 



SECRETING GLANDS 



[CH. XXIX. 



communicate with the exterior. The principal tracts are the Digestive, 

 Respiratory, and Genito -urinary. 



Secreting glands may be classified according to certain types, 

 which are the following : 1. The simple tubular gland (A, fig. 392), 

 examples of which are furnished by the crypts of Lieberkiihn in the 



FIG. 392. Diagram of types of secreting glands. A, simple glands, viz., g, straight tube; h, sac; i, 

 coiled tube. B, multilocular crypts ; fc, of tubular form ; I, saccular. c, racemose, or saccular 

 compound gland ; m, entire gland, snowing branched duct and lobular structure ; n, a lobule, 

 detached with o, branch of duct proceeding from it. D, compound tubular gland. (Sharpey.) 



intestinal wall. To the same class may be referred the elongated and 

 tortuous sudoriferous glands. 



2. The compound tubular glands (D, fig. 392) form another 

 division. These consist of main gland-tubes, which divide and 

 sub-divide. 



3. The racemose glands are those in which a number of vesicles 

 or acini are arranged in groups or lobules (c, fig. 392). The Meibo- 



