STEUCTUKE OF SECRETING GLANDS. 



long and tubular in character ; lie proposes accordingly to group them along with such glands 

 as the kidney and testicles as compound tubular glands. But since, as Chievitz has shown, 

 the salivary and other similar glands, exhibit at an early condition of development a markedly 

 sacculated character, the ultimate (tubular) alveoli being formed later as outgrowths of the 

 saccules, whereas the tubular glands proper never exhibit this sacculated character, it appears 

 desirable still to recognise a morphological difference between the two classes of glands. 



459 



460 



462 



Fig. 458. SIMPLE SACCULAR GLAND FROM THE AMPHIBIAN SKIN. (Flemming. ) 



Fig. 459. SIMPLE TUBULAR GLAND FROM THE HUMAN INTESTINE. (Flemming. ) 



Fig. 460. DIAGRAM OF SMALL ACINOUS GLAND FORMED OF A SIMPLE "DUCT-SYSTEM." (Flemming.) 



461. PART OF A SMALL "RACEMOSE" MUCOUS GLAND OF THE TONGUE, SHOWING THE TUBULAR 

 CHARACTER OF THE ALVEOLI. (Flemming.) 



Fig. 462. CONSTRUCTION OF A LOBULE OF AN "ACINOUS" GLAND. (Kolliker. ) 



a, duct ; b.b, branches of duct ; c, alveoli as they lie together in the gland ; d, the same unravelled, 

 showing their connection as an irregular tube. 



The acinous, racemose or aciiio tubular compound glands (fig. 457, c) are 

 composed of a multitude of alveoli, opening in clusters into the extremities of a 

 branched tube, named the excretory duct. The alveoli are saccular, pyriform or 

 tubular. They are often rather filled than lined by secreting cells ; and are arranged 

 in groups, round the commencing branches of the duct, with which their cavities 

 are continuous (fig. 457, c). The ultimate branches of the duct open into larger 

 branches (0), these into larger again, till they eventually terminate in one or more 

 principal excretory ducts (m), by which the secretion is poured out of the gland. It is ? 

 as we have seen from the clustered arrangement of their ultimate recesses, that these 

 glands are named " racemose " or grape-like ; and they, for the most part, have a dis- 



