34 SECKETION OF BUCCAL AND LINGUAL GLANDS. [BOOK II. 



fluctuates approximately between the same limits as in the case of 

 the submaxillary secretion, and the proportion of organic constituents 

 in the former is appreciably less than in the latter. The cause of 

 the greater viscidity of the sublingual saliva is believed by Werther 

 to be its neutral or barely alkaline reaction, carbonate of soda not 

 occurring in determinable quantity amongst its mineral constituents. 

 The viscidity of solutions of mucin is known to be connected with, 

 or to depend upon, the alkalies which they contain, for if these be 

 neutralised the solutions become more and more diffluent until the 

 point at which excess of acid precipitates mucin. Whilst the organic 

 matters are in small amount, the proportion of other salts and 

 especially of NaCl in sublingual is much larger than in submaxillary 

 saliva. Whilst the amount of sodium chloride in the blood amounts, 

 according to Sertoli, to 0*59 per cent., in sublingual saliva the 

 chlorine present, calculated as sodium chloride, corresponds to 1 per 

 cent, of this salt. 



Appended is a table drawn from Werther's memoir which exhibits 

 the amount of the saliva of the parotid, submaxillary and sublingual 

 saliva collected in stated times, together with the results of their 

 analysis 1 . 



5. THE SECRETION OF THE GLANDS OF THE Mucous MEMBRANE 



OF THE MOUTH AND TONGUE. 



Opening on the surface of the mucous membrane lining the 

 lips and cheeks are certain compound racemose glands, the so-called 

 labial and buccal glands ; in addition, large numbers of glands, some 

 of which have the structure of serous, others of mucous glands, 

 open on the surface of the mucous membrane of the posterior 

 part of the tongue. The combined secretion of all these glands 

 adds itself to the fluid poured into the mouth by the salivary 

 glands. We have not, unfortunately, any reliable information upon 

 the character of the mixed secretion, much less as to that of any one 

 of these sets of glands. 



The only researches which have been carried out on this subject 

 have consisted in preventing the secretions of the salivary glands 

 from reaching the mouth, either by ligature of their ducts, or by 

 causing them to discharge their contents externally, and examining 

 the secretion then present in the mouth. 



Under these circumstances the mouth has been found to be un- 

 usually dry, and a small quantity of tough mucus is secreted. 

 Bidder and Schmidt 2 found this to have the following composition : 



1 Moritz Werther, 'Einige Beobachtungen tiber die Absonderung der Salze in 

 Speichel' (Aus dem physiologischen Institut zu Breslau). Pfluger's Archiv, Vol. 38 

 (1886), p. 293. 



2 Bidder and Schmidt, quoted by Kiihne (Lehrbuch der Physiologischen Chemie, p. 

 16), and by Maly. The author has been unable to discover the original source, as it 

 does not occur in the classical work by these Authors entitled Die Verdauung nach 

 Versuchen. 



