9O THE TISSUES. 



1 . Coiled Tubular Gland. The secreting portion of the tubule 

 may be coiled up into a compact mass ; 



2. Simple Branched Tubular Glands. Several tubules, which 

 may be either branched or unbranched, and which may vary greatly 

 in length, may unite in one duct, which carries to the surface the 

 secretion of all the tubules connected with it ; 



3. Compound Branched Tubular Glands. Glands of this type 

 consist of a varying number of simple branched tubular glands, the 

 ducts of which unite to form a common duct (Fig. 52); 



Fig. 54. Schematic diagram of glandular classification : I, Simple tubular gland; 

 2, simple tubular gland with coiled secreting portion ; 3, 4, 5, types of simple branched 

 tubular glands ; 6, compound branched tubular gland ; 7, 8, types of simple branched 

 tubulo-alveolar glands ; 9, simple alveolar gland; 10, II, types of simple branched alve- 

 olar glands ; 12, compound branched alveolar gland ; 13, type of follicular gland ; 14, 

 reticular gland, the shaded portions representing anastomosing tubules. 



4. Reticulated Tubular Glands. In certain of the branched 

 tubular glands the secreting tubules anastomose with each other, 

 forming a reticulated gland (Fig. 53) ; 



5. Tubulo-alveolar Gland. The secreting surface of tubular 

 glands may be further increased by the formation of small and 

 variously shaped protuberances or saccules, known as alveoli, 

 which may be situated at the end or on the sides of the tubules, 

 and are lined by secretory epithelium and empty the secretion 



