SALIVA. 



variety of saliva and its special connection with deglutition, it is supposed to be secreted 

 immediately before and during the act of swallowing. The experiments which are ad- 

 vanced in support of this view are mostly those in which a tube was fixed in each of the 

 three salivary ducts in a dog, when the animal was caused to make movements of the 

 jaw, movements of deglutition, and at the same time the gustatory nerves were stimu- 

 lated by the introduction of vinegar into the mouth. In an experiment of this kind it 

 was observed that fluid was secreted by all the glands, but in unequal proportions; "the 

 submaxillary saliva flowed very abundantly, the parotid saliva much less, and the sublin- 

 gual saliva flowed very feebly." Although the animal made movements of mastication, 

 experienced a gustatory impression, and made movements of deglutition, it is by no means 

 evident from this observation, or from others reported by Bernard, that the flow of the 

 sublingual saliva had any special connection with the act of deglutition. The observa- 

 tions of Colin on this subject show that, in the domestic ruminants, there is a constant 

 flow of the sublingual saliva during the time occupied in eating. 



It has been experimentally demonstrated that the sublingual glands may be excited 

 to secretion by impressions made by sapid substances upon the nerves of taste, although 

 the flow is always less than from the submaxillary glands. The great viscidity of the 

 sublingual saliva renders it less easily mixed with the alimentary bolus than the secre- 

 tions from the parotid or the submaxillary glands. 



Fluids from the Smaller Glands of the Mouth, Tongue, and Pharynx. Beneath the 

 mucous membrane of the inner surface of the lips, are small, rounded, glandular bodies, 

 opening by numerous ducts into the buccal cavity, called the labial glands ; and, in the 

 submucous tissue of the cheeks, are similar bodies, called the buccal glands. The latter 

 are somewhat smaller than the labial glands. Two or three of the buccal glands are of 

 considerable size and have ducts opening opposite the last molar tooth. These are 

 sometimes distinguished as the molar glands. There are also a few small glands in the 

 mucous membrane of the posterior half of the hard palate ; but the glands on the under 

 surface of the soft palate are larger and more numerous and here form a continuous 

 layer. The glands of the tongue (lingual glands) are situated beneath the mucous mem- 

 brane, mainly on the posterior third of the dorsum ; but a few are found at the edges 

 and the tip. All of these are small, racemose glands, similar in structure to those which 

 have been called the true salivary glands. In addition to these structures, the mucous 

 membrane of the tongue is provided with a number of simple and compound follicular 

 glands, which extend over its entire surface but are most abundant at the posterior por- 

 tion, behind the circumvallate papilla?. 



In the pharynx and the posterior portion of the buccal cavity, are found the pharyn- 

 geal glands and the tonsils. In the pharynx, particularly the upper portion, racemose 

 glands, like those found in the mouth, exist in large numbers. The mucous membrane is 

 provided, also, with numerous simple and compound mucous follicles. The tonsils, situ- 

 ated on either side of the fauces between the pillars of the soft palate, consist of an ag- 

 gregation of compound follicular glands, held together by fibrous tissue. The number of 

 glands entering into the composition of each tonsil is from ten to twenty. 



The secretion from the glands and follicles above enumerated cannot be obtained, in 

 the human subject, unmixed with the fluids from the true salivary glands. It has been 

 obtained, however, in small quantity, from the inferior animals, after ligature of all the 

 salivary ducts. This secretion is simply a grayish, viscid mucus, containing a number of 

 leucocytes and desquamated epithelial scales. It is this which gives the turbid and opa- 

 line character to the mixed saliva, as the secretions of the various salivary glands are all 

 perfectly transparent. The fluid from these glands in the mouth is mixed with the sali- 

 vary secretions ; and that from the posterior part of the tongue, the tonsils, and the 

 pharyngeal glands passes down to the stomach with the alimentary bolus. This secretion, 

 consequently, forms a constant and essential part of the mixed saliva. 

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