CHAP. XXIII.] THE PHARYNX AND PALATE. 185 



stomach ; and Spallanzani observed that aliments enclosed in per- 

 forated tubes, and introduced into the stomachs of living animals, 

 were earlier digested when previously mixed with saliva, than with 

 water. 



Dr. Wright injected saliva into the blood-vessels of dogs, and 

 found the animals dying in a few days or weeks, with symptoms 

 much resembling those of hydrophobia. In other instances, where 

 he employed white of egg, isinglass, and mucus, no such effects 

 ensued.* * 



Of Deglutition. The parts concerned in this act are the mouth, 

 the pharynx, and the oesophagus, the two latter of which remain to 

 be considered. 



The pharynx, as usually described, consists of all that cavity 

 lined with mucous membrane which is situated in front of the 

 cervical vertebrae, behind the nose, mouth, and larynx, below the 

 base of the skull, and above the oesophagus. This cavity, however, 

 as we shall shew, comprises two parts entirely distinct from one an- 

 other : an upper, with its walls never in contact, lined with ciliated 

 epithelium and containing air, which we shall term the respiratory 

 compartment, being, in fact, strictly a portion of the air-passages ; 

 and a lower, dilatable and contractile, lined with scaly epithelium, 

 and giving passage to the food from the mouth to the oesophagus, 

 which we shall term the alimentary compartment, as it is a portion 

 of the alimentary tube. The air-passages are interrupted between 

 the upper compartment and the glottis, and in this interval the air 

 has to traverse the lower or alimentary compartment in its course 

 from the nose to the lungs. The alimentary and respiratory tubes 

 may thus be said to intersect each other in this common cavity, a 

 fact of leading importance to the understanding of the anatomical 

 arrangement of these parts. Not to speak of the laws of develop- 

 ment to which this free communication of the two great tracts 

 ministering to the nutrient function may be referrible (a commu- 

 nication still freer previous to the fusion of the sides of the palate 

 at an early stage of foetal existence) , it may be sufficient to allude 

 to the great end answered by it, viz., the bringing the whole appa- 

 ratus of the mouth into connexion with the lungs for articulation 

 and speech, and to the subordinate object of much heightening the 

 sense of taste during mastication, by allowing the odour of the 

 food to ascend from the mouth and pharynx to the olfactory region 

 through the posterior nares. (See vol. i. p. 446.) 



* Lancet, 1844. Br. and For. Med. Rev., Jan. 1847. 



