344 CHEMISTR Y OF THE DIGESTIVE PROCESSES. 



quantitative analysis, but made out that it was a clear slimy fluid of 

 stronger alkaline reaction than submaxillary saliva, and containing 

 mucin, diastatic ferment, and sulphocyariide. 



The sublingual saliva of the dog is a viscous, scarcely fluid mass ; it contains 

 salivary corpuscles, but is otherwise quite clear and transparent, is alkaline in 

 reaction, and contains 2*75 per cent, of total solids. 1 Werther 2 has analysed 

 the sublingual saliva of the dog, and finds that its great viscidity is not due 

 to any excess of organic constituents ; he attributes it to the reaction which he 

 found to be neutral or barely alkaline. The proportion of inorganic salts is 

 much larger than in parotid or submaxillary saliva. 



Secretion of the raucous glands of the mouth. This has not 

 been obtained in man. In the dog ithas been obtained by ligaturing 

 the ducts of all the salivary glands, or by extirpating the salivary 

 glands. The amount secreted is exceedingly small ; it is a thick ropy 

 mucus of alkaline reaction, full of fragments of epithelial and mucous 

 cells, and containing about 1 per cent, of total solids. 3 



The mixed saliva. Mixed saliva may easily be obtained from the 

 mouth by depressing the head . and everting the lower lip ; or by 

 depressing the head, keeping the mouth widely open, and avoiding 

 all attempts to swallow. It is a clear, viscid, and very slightly 

 opalescent fluid, which froths easily. It is normally alkaline in 

 reaction; when it is acid this reaction is commonly due to fer- 

 mentation of particles of food in the mouth. The alkalinity is least 

 when fasting, as in the morning before breakfast, and reaches its 

 maximum with the height of secretion during, or immediately after 

 eating. According to Chittenden and Ely, 4 the alkalinity is equiva- 

 lent to that of a solution containing 0*08 per cent, of sodium carbonate 

 (Na 2 Co 3 ). 



The quantitative composition of mixed saliva is very variable, as 

 might be expected from the difference in composition of the secretions 

 which form it, and the varying proportion in which these must be pre- 

 sent in different samples. The amount of total solids in human saliva 

 varies normally between 5 and 10 parts per 1000 ; the specific gravity 

 between 1'002 and 1'OOS. 



Organic constituents. The organic matter is partially in suspension, 

 and partially in solution. The suspended matter consists of squamous 

 cells detached from the epithelium of the mouth, and of the sali- 

 vary corpuscles, which are leucocytes altered by the action of the 

 saliva, and containing granules which exhibit in fresh saliva active 

 Brownian movements. The dissolved organic matter consists of 

 mucin, ptyalin, and traces of proteids ; the amount of the latter is 

 so small that it cannot be quantitatively estimated. Saliva is also 

 said to contain normally minute traces of urea; but the amount 

 is so small that such a statement cannot be made with certainty. 

 In pathological conditions the amount of urea present may, however, 

 become very appreciable. Leucine and lactic acid are found under 



1 Heidenhain, Stud. d. physiol. Inst. zu Breslau, Leipzig, Heft 4. 



2 Arch. f. d. ges. Physiol., Bonn, 1886, Bd. xxxviii. S. 293. See also Langley and 

 Fletcher, Phil. Trans., London, 1887, vol. clxxx. p. 109. 



3 Bidder and Schmidt, "Die Verdauungssafte," Mitau und Leipzig, 1852, S. 5. 



4 Am. Chem. Journ., Baltimore, 1883, p. 329. See also Werther, Arch. f. d. ges. Physiol., 

 Bonn, 1886, Bd. xxxviii. S. 293. 



