220 AN AMERICAN TEXT-BOOK OF PHYSIOLOGY. 



The secreting tubules of the salivary glands possess distinct lumens 

 round which the cells are arranged. In addition a number of recent observers, 

 making use of* the Grolgi method of staining, have apparently demonstrated 

 thai in the albuminous glands the Lumen is continued as fine capillary spaces 

 running between the secreting cells. 1 The statement is also made that 1'rom 

 these secretion capillaries small side-branches are given off that penetrate 

 into the substance of the cell, making an intracellular origin of the system of 

 duets ; this point, however, needs confirmation. In the mucous glands similar 

 secretion capillaries an' found only in connection with the demilunes. This 

 latter fact supports the view that the demilunes are not simply inactive forms 

 of mucous cells, hut cells with a specific functional activity. It is an nu- 

 ll. ml)ted fact that the salivary glands possess definite secretory nerves which 

 when stimulated start the formation of secretion. This fact indicates that 

 there must be a direct contact of some kind between the gland-cells and the 

 terminations of the secretory fibres. The nature of this connection has been 

 the subject of numerous investigations, the results of which were for a long time 

 negative or untrustworthy. More recently, however, the application of the 

 useful Gol«;i method has led to satisfactorv results. The ending of the nerve- 

 fibres in the submaxillary and sublingual glands has been described by a num- 

 ber of observers. 2 The accounts differ somewhat as to details of the finer 

 anatomv, but it seems to be clearly established that the secretory fibres from 

 the chorda tympani end first round the intrinsic nerve-ganglion cells of the 

 glands, and from these latter cells axis-cylinders are distributed to the 

 secreting cells, passing to these cells along the ducts. The nerve-fibres termi- 

 nate in a plexus upon the membrana propria of the alveoli, and from this 

 plexus fine fibrils pass inward to end on and between the secreting cells. 

 It would seem from these observations that the nerve-fibrils do not penetrate 

 or fuse with the gland-cells, as was formerly supposed, but form a terminal 

 network in contact with the cells, following thus the general schema for the 

 connection between nerve-fibres and peripheral tissues. 



Composition of the Secretion. — The saliva as it is found in the; mouth 

 is a mixed secretion from the large salivary elands and the numerous 

 smaller glands scattered over the mucous membrane of the mouth. It is a 

 colorless or opalescent, turbid, and mucilaginous liquid of weakly alkaline re- 

 action and a specific gravity of about 1003. It may contain numerous flat 

 c,ll~ derived from the epithelium of the mouth, and the peculiar spherical cell- 

 known as salivary corpuscles, which seem to be altered leucocytes. The im- 

 portant constituents of the secretion are mucin, a diastatic enzyme known as 

 ptvalin, traces of albumin and of potassium sulphocyanide, and inorganic salts 

 such a- potassium and -odium chloride, potassium sulphate, sodium carbonate, 

 and calcium carbonate and phosphate. The average proportions of these con- 

 stituent- is given in the following analysis by Hammerbacher : 



1 Laserstein: Pfliiger'a Archiv fur die gesammte Physiologie, 1893, Bd. ■">•">, S. 417. 

 • Huber : Journal of Efi>rrhncnt<il Medicim, ls'.it',, vol. i. ]>. "J*l. 



