TYPICAL STRUCTURE OF ORGANS 



31 



loosely the spaces between the individual grapes and the 

 branches of the stem, we shall have something with which 

 to compare the arrangement of the connective tissue in 

 relation to the rest of the gland the sawdust standing 

 for the connective tissue in which the ducts and alveoli 

 are embedded, and the basket for the capsule. 



Duct 



Alveoli 



Secreting Cells 

 Capillary Network 



FIG. 21. The origin of the duct of a gland in alveoli, together with the 

 connective tissue and blood vessels 



4. Minute structure of ducts and alveoli. The alveoli are 

 not, however, empty shells like glass flasks nor solid masses 

 like grapes, but rather hollow bags lined with a layer of 

 thickish, closely set cells, all much alike. Each of these cells 

 consists of two portions a small central body, the nucleus, 

 and a larger surrounding mass, the cytoplasm. All organs 

 of the' body are composed of cells, differing in different 

 organs or in different parts of the same organ (as in the 

 duct and the alveolus of the gland), but all consisting of two 

 never-failing parts nucleus and cytoplasm. 



