83 



like all other albuminous fluids, it froths when agitated, by absorbing 

 oxygen, for which it appears to have a strong affinity. Its affinity for 

 oxygen is such, that one may oxydize gold and silver, by triturating 

 in saliva, thin leaves of those metals which are of such difficult oxy- 

 dizement. 



The irritation occasioned by the presence or the desire of food, excites 

 the salivary glands; they swell and become so many centres of fluxion, 

 towards which the humours flow abundantly*. Bordeu first called the 

 attention of physiologists, to the great quantity of nerves and vessels re- 

 ceived by the parotid, maxillary and sublingual glands, from the carotid, 

 maxillary and lingual arteries, from the portio dura of the seventh pair of 

 nerves, from the lingual nerve of the fifth pair, which penetrate their sub- 

 stance, or pass over a portion of their surface. This great number of 

 vessels and nerves is proportioned to the quantity of saliva which is se- 

 creted, and this is estimated at about six ounces during the average time 

 of a meal. It flows in greater quantity, when the food that is used is 

 acrid and stimulating: it mixes with the mucus, copiously secreted with 

 the mucous, buccal, labial, palatine, and lingual glands, and with the se- 

 rous fluid, exhaled by the exhalent arteries of the mouth. The saliva 

 moistens, imbues, and dissolves the ball formed by the aliment, brings to- 

 gether its divided molecules, and produces on them the first change. 

 There can be no doubt, that the saliva mixing with the food by the mo- 

 tion of the jaws, absorbs oxygen, and unites to the alimentary substances, 

 a quantity of that gas fit to bring about the changes which they are ult> 

 mately destined to. undergof. 



* The intimate sympathy or consent of action that exists between the functions of 

 the stomach and the salivary apparatus, by means of the nerves which chiefly preside 

 over the process of digestion and all the operations of secretion and nutrition, is strong-. 

 ly evinced by the following 1 fact. An individual, in an attempt to commit suicide, divi- 

 ded the oesophagus to a considerable extent. During the attempts to preserve his exist- 

 cnce, food was conveyed into the stomach by means of a tube. As soon as the aliments 

 were received into this viscus, the salivary secretion became abundant, although the 

 process of mastication was not, of course, attempted. Copland. 



f The specific gravity of saliva is 1,038. It mixes with water only by trituration, has 

 a. strong affinity for ox\gen, absorbs it readily from the air, and gives it out again to 

 ether bodies. Whether it possesses any affinity for nitrogen, has not been shown ; nor 

 has the absorption of oxygen by this fluid, during t'.ie process of mastication, been suf- 

 ficiently attended to in our speculations respecting the pi-ocess of digestion. We can 

 hardly suppose that it takes up oxygen without a portion of nitrogen, or of common air. 

 If any quantity of the latter be mixed with it during the insalivation of the food, an evi- 

 dent source is disclosed from which nitrogen may be conveyed into the circulating 1 

 fluids, in addition to that which is derived from the ordinary aliments. 



The affinity which the saliva has for oxygen, and the readiness with which it gives 

 out this substance to other bodies, explains the reason why gold or silver triturated with 

 it is oxydized ; and why mercury soon disappears when triturated with saliva. Hence, 

 also, the reason why the application of saliva to sores is an useful remedy, and one to. 

 which the lower animals have constant recourse. 



The constituents of saliva, according to BE RZ EMUS, are as follows : 



Water, 992.9 



Peculiar animal matter (precipitated by acet. plumbi) mucus of BOSTOCK, 2.9 



Mucus* albumen of BOSTOCK and TUOMPSOX, 1.4 



Alkaline muriates, 1.7 



Lactate of soda and animal matter, 0.9 



Pure soda, : 0.2 



1000.0 



* The mucous or albuminous portion lias all the characters of albumen. On incine- 



