MASTICATION AND DEGLUTITION. 



73 



" The excretion of saliva, amounting, according to the arbi- 

 trary statement of Nuck , to a pound in twelve hours, is aug- 

 mented by stimuli and by mechanical pressure, or, if the term 

 may be allowed, emulsion. .-,^ 



" The latter cause, greatly favoured by the situation of the 

 parotids, at the articulation of the jaws, occurs when we chew 

 hard substances, which thus become softened. 



" The former occurs when acrid substances are taken into 

 the mouth, which are thus properly diluted ; or arises from ima- 

 gination, as when the mouth waters during the desire for food. 



" The mucus of the labial and buccal glands , and of the 



Inner part of lips. 

 a a, labial glands : 6, buc- 

 cal glands : c c, parotid 

 ducts : d d, their orifices. 



tongue, as well as the moisture which transudes from the soft 

 parts of the mouth, is mixed with the saliva. 



" The mixture of these fluids with a substance which we are 

 chewing, renders it not only a pultaceous and easily swallowed 

 bolus, but likewise prepares it for further digestion and for assi- 

 milation. 



" The mechanism p of deglutition, although very compli- 

 cated, and performed by the united powers of many very 

 different parts, amounts to this : the tongue being drawn 

 towards its root, swelling and growing rigid, receives the bolus of 

 food upon its dorsum, which is drawn into a hollow form. The 

 bolus is then rolled into the isthmus of the fauces, and caught 

 with a curious and rather violent effort by the infundibulum of 

 the pharynx, which is enlarged and in some measure drawn for- 

 ward to receive it. The three constrictores <i muscles of the 

 pharynx drive it into the oesophagus. These motions are all per- 



" Nuck, Sialographia, p. 29. sq." 



" De Courcelles, 1. c. tab. iv. e. e. e." 



p " Fr. Bern. Albinus, De Deglutitione. LB. 1740. 4to. 



P. J. Sandifort, Deglutitionis Mechanismus. Lugd. Batav. 1805. 4to." 



1 " Eustachius, tab. XLII. fig. 4. 6. 



Santorini, Tab. Posthum. vi. fig. 1. 

 . B. S. Albinus, Tab. Muscular, xii. fig. 23, 24." 



