GLAND TISSUES 9 



a bunch of grapes upon their stem racemose gland. The salivary 

 and pancreatic glands resemble this form. 



The secretion of a true gland is discharged through a duct 

 which opens upon some surface, either of the exterior or the in- 

 terior of the body for instance, the sweat glands open upon the 

 skin, the gastric glands open upon the interior surface of the 

 stomach, etc. All secretions which are discharged through ducts 

 of glands are called external secretions. (For internal secretions 

 see page 263.) 



Lymphoid tissues are so called because they contain lymph 

 cells supported in a network of retiform tissue. The faucial or 



Excretory duct. 



Secretory duct. 



Intercalated duct. 



End pieces. 



FIG. 6 DIAGRAM. OF VARIOUS FORMS OF GLANDS. (Lewis and St&hr.) 

 The arrangement of ducts in D is that of the human submaxillary gland. 



palatine tonsils are lymphoid in structure (page 133), as are 

 also the lingual and thenaso-pharyngeal tonsils (page 135). (Ade- 

 noids are hypertrophied naso-pharyngeal tonsils.) 



Blood and lymph, although quite different in composition from 

 others, still conform to the definition of a tissue and are called 

 fluid tissues. They are each composed of an assemblage of small 

 cells supported by intercellular substance; in this case, the inter- 

 cellular substance is fluid instead of solid or semi-solid. In blood, 



