16 MIXED SALIVA. [BOOK II. 



not necessarily so : the stored-up matter previously referred to is 

 converted into soluble constituents of the secretion, and at the same 

 time there occurs a growth of the protoplasm of the cells, at the 

 expense doubtless of the richer supply of lymph which, during the 

 secretory act, bathes the gland. 



The period of activity in so far as the gland cell is concerned is 

 indeed a period of removal of ready-made constituents of secretion; 

 a period in which the protoplasmic constituents of the cells generally 

 increase. According to some, active proliferation of secreting cells 

 occurs ; the latter statement is probably incorrect. 



Whilst we have in a few sentences sketched the general characters 

 of the changes which glands undergo during secretion, our picture 

 is wanting in all details, and the reader is referred for further infor- 

 mation to works on Histology and Physiology 1 . 



SECT. 2. THE CHEMICAL COMPOSITION OF MIXED SALIVA, OF THE 

 SECRETION OF THE THREE CHIEF SALIVARY GLANDS, AND OF 

 BUCCAL Mucus. 



1. MIXED SALIVA. 



Mode of ob- The mixed saliva of man may be obtained in a state 

 taining mixed of purity, some hours after a meal, by everting the lower 

 saliva. \{p } depressing the head, and collecting the clear liquid 



which slowly trickles from the angles of the mouth. An abundant 

 flow of saliva may be provoked by the internal use of Jaborandi 

 or its alkaloid Pilocarpine. 



A fairly copious flow may be obtained by inspiring, through the 

 mouth, the vapour of chloroform, or by washing out the mouth with 

 water containing a little ether in solutiorj, or even by chewing a 

 fragment of rhatany root ; in the latter case the fluid is naturally 

 mixed with the vegetable fragments, and with the soluble constituents 

 of the drug. 



Quantity of In the case of saliva, as in that of other digestive 

 saliva secre- juices, we possess no mode of determining in a reliable 

 ted by man. manner the amount of the secretion which is poured 

 out in the physiological condition. 



Mitscherlich calculated the probable secretion of mixed saliva to 

 amount to 8 to 10 ozs. daily. 



According to Tuczek 2 , the salivary glands of adult man secrete 



1 Consult specially Heidenhain's systematic account under the heading ' Vorgange 

 innerhalb der Driisen wahrend ihrer Thiitigkeit' in Hermann's Handbuch, Vol. v. 

 Chapter iv. p. 56. The reader will find a more lengthy treatment than is possible in 

 the present work in Dr Michael Foster's Text-Book of Physiology, Ed. v. 



2 Tuczek, ' Ueber die von Menschen wahrend des Kauens abgesonderten Speichel- 

 mengen.' Zeitschr. f. Biologic, Vol. xn. p. 534. 



