344 CHE MIS TR 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 sulphocyanide. 
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 mucous glands of the mouth. — This has not 
been obtained in man. In the dog it has 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 1-008. 
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 Hcidenhain, 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, 18S7, vol. clxxx. p. 109. 
3 Bidder and Schmidt, "Die Yerdauungssafte," Mitau mid Leipzig, 1852, S. 5. 
4 Am. Chem. Joum., Baltimore, 1883, p. 329. See also Werther, Arch. f. d. gcs. Physiol., 
Bonn, 1886, Bd. xxxviii. S. 293. 
