550 OF SECRETIOX. 



the saliva examined directly before and during the act of eating, is always 

 alkaline. It may be doubted whether the add reaction is not due to the mucus 

 of the mouth; which, at times when only a small amount of saliva is excreted, 

 is not neutralized by its alkali. Its specific gravity varies from 1-006 to 1-009. 

 It contains a small number of corpuscles, which seem to be partly epithelium- 

 cells from the mucous surface of the mouth, and partly the secreting cells of 

 the salivary vesicles. The solid matter contained in Saliva is estimated by Ber- 

 zelius at about 1 per cent. The animal principles of which this is composed 

 are osmazome, mucus, and a peculiar substance termed salivary matter, which 

 is soluble in water, insoluble in alcohol, and yet is different from either albu- 

 men or gelatin. Clear Saliva, when submitted to the influence of galvanism, 

 is found to exhibit a faint coagulum ; and hence it has been supposed to con- 

 tain albumen. The presence of this substance, however, is doubtful. A con- 

 siderable proportion of saline and earthy matter exists in the solid residue of 

 saliva ; this is nearly of the same character as that which the blood contains, 

 being chiefly composed of the phosphate of lime and soda, the chlorides of 

 sodium and potassium, and the lactates of soda and potash. One remarkable 

 property of the salivary secretion, is its formation of a rust-red precipitate 

 when mixed with a solution of a per-salt of iron. This is supposed to be due 

 to the presence in it of the principle termed sulpho-cyanogen. The tartar which 

 collects on the human teeth consists principally of the earthy phosphates, the 

 particles of which are held together by about 20 per cent, of animal matter ; 

 and nearly the same may be said of the salivary concretions which occasionally 

 obstruct the ducts.* It appears from the recent experiments of Schulze, Leh- 

 mann, and others on the continent, and of Dr. Wrightt in this country, that the 

 peculiar animal .matter of the saliva has a decided effect in metamorphosing 

 certain alimentary substances, and thus performs the first part of the digestive 

 process. It appears unquestionable, that starch may be converted into sugar, 

 and sugar into lactic acid, by its agency ; and that if concentrated, it has a 

 certain solvent power for casein, animal flesh, and other albuminous substances. 

 But these facts by no means justify the conclusion which has been drawn 

 from them, that the Saliva is the real agent in Digestion, and that no solvent 

 fluid is secreted by the stomach itself; a conclusion to which many well-known 

 facts are opposed, and completely subverted by the observations of Dr. Beau- 

 mont, by whom the secretion of gastric fluid has been seen to be poured out 

 from the walls of the stomach. 



695. The Pancreatic Secretion of Man cannot, of course, be readily obtained 

 for analysis ; that which is procured from the lower animals, however, probably 

 gives a sufficiently correct idea of its character. It seems to be of a nearly 

 similar nature with saliva, but contains a much larger proportion of solid mat- 



* [From analyses, conducted on the same plan as those of the blood, Enderlin (Annalen 

 der Chemie und Pharmacie, Marz, 1844) concludes that the saliva, like the blood, contains 

 no lactate, carbonate, or acetate; but that its alkaline reaction is due to tribasic phosphate 

 of soda, which serves also as the solvent of the mucous and proteine-compounds. The 

 analysis of the ashes obtained from a very large quantity, afforded, in 100 parts : 

 Tribasic phosphate of soda (3 Na.'O, P 2, O 5) . . . 28.122 



Chlorides of sodium and potassi-um .... 61-93 



Sulphate of soda . . . . . . .2-315 



Phosphate of lime "^ 



" magnesia V- . . . . 5-509 



" iron 3 



He believes, from this, that the saliva must take a very important part in digestion. And 

 it is but reasonable to connect these'-dis.cdveries of the basic phosphate of the saliva and 

 the acid phosphate of the gastric fluid, with the fact observed by Schultz and Lehmann, 

 and more clearly by Dr. Wright, (see Ia1*t .Report, p. 12, and Lancet, 1842-3) that the alka- 

 linity of the saliva bears a direct proportfon to the acidity of the gastric secretion. M. C.] 

 f Lancet, March 5, 1842, et seg. 



