08 



PHYSIOLOGY 



CHAP. 



sublingual. They are glands of the racemose type, i.e. they 

 consist of acini, which are more or less saccular or tubular in 

 shape, their cavities or alveoli communicating with one another 



by one or more branching excretory 

 ducts. The acini are surrounded by 

 a basement membrane consisting of 

 a network of flattened, nucleated, 

 branching cells, the meshes of which 

 are occupied by a delicate homo- 

 geneous substance. Inside the base- 

 ment membrane (Fig. 18) the secreting 

 cells form an epithelial lining which 



Fie. 18. Membrana propria of two l-, mnlr ](, f} 1p .,1 V pnlnr pq vitv Thp 

 alveoli isolated. From orbital gland DOUndS tne diveolai Cavity. 



of puppy. (Lavdowsky.) 



are united into lobules, either by 

 blood-vessels or by loose connective 

 many lymph spaces and a rich network 



tissue, which contains 

 of blood capillaries. 



Two kinds of secreting cells can be distinguished in the alveoli, 

 the serous or albuminous, and the mucous (Heidenhain). The 

 serous cells, which secrete 

 a thin fluid 

 serum - albumin, 

 in the restin 



* \ "L-r 



containing 

 exhibit 

 state a 



protoplasm so richly infil- 

 trated with granules that 

 the nucleus is obscured 

 and becomes invisible. 

 The mucous cells, which 

 secrete a fluid that is ropy 

 from the large amount of 

 mucin, are large, clear, 

 and spheroid when the 

 gland is resting. They 

 almost fill the alveolar 

 cavity, their nuclei being 

 invisible because they lie 

 close to the basement 

 membrane, and are 

 pressed against it (Fig. 



19). When all the alveoli 

 f J 1-1 -j.i 



of a gland are lined with 



albuminous cells (e.g. the 



parotid in man and almost all mammals, the submaxillary of rabbits, 



and certain glands that are scattered in the buccal niucosa), the 



gland, as a whole, is termed albuminous ; when the alveoli are 



lined with mucous cells alone (e.g. part of the submaxillary in man, 



and the sublingual in all animals, and many simple buccal glands) 



Fl(: . p.,._ s ,. ctiou of part of huill ,,,, sullimxnia ,. y g]an , L 



(Heidcnliam.) On the right, a group of mucous alveoli 

 with demilunes of Gianuuzzi ; on the left, a group of 



serous 



