188 DIGESTION". 



The mucous membrane of the oesophagus is attached to 

 the muscular tissue by a dense fibrous layer. It is quite vas- 

 cular and reddish above, but becomes gradually paler in 

 the inferior portion. The mucous membrane is ordinarily 

 thrown into longitudinal folds, which are obliterated when the 

 tube is distended. Its epithelium is thick, of the pavement 

 variety, and is continuous with, and similar to the cover- 

 ing of the lower portion of the pharynx. It is provided with 

 papillse of the same structure as those found in the pharynx, 

 the conical variety predominating. Numerous small race- 

 mose glands are found throughout the tube, forming by their 

 aggregation at the lower extremity, just before it opens into 

 the stomach, a glandular ring. 



Mechanism of Deglutition. For convenience of descrip- 

 tion, physiologists have generally divided the process of deg- 

 lutition into three periods. The first period is occupied by 

 the passage of the alimentary bolus backward to the isthmus 

 of the fauces. This may appropriately be considered as a dis- 

 tinct period, because the movements are effected by the action 

 of muscles entirely under the control of the will. The second 

 period is occupied by the passage of the food from the isthmus 

 of the fauces, through the palate, into the upper part of the 

 oesophagus. The third period is occupied by the passage of 

 the food through the oesophagus into the stomach. 



In the first period, the tongue is the important agent. 



ocular proof of the inaccuracy of the assertion made by Sappey. In the human 

 oesophagus, there is a manifest difference in color between the upper and lower por- 

 tions. Above, the color is red ; and below, it becomes paler and more like the in- 

 voluntary muscular tissue. A specimen taken from any of the deep-red portions 

 shows the striae of the red muscular fibres with a inch objective as distinctly as 

 could be desired. Passing down the tube, small bands of this red tissue are 

 seen, which likewise present, on microscopic examination, the striated muscular 

 fibre. These we demonstrated down as far as the diaphragm ; though in the 

 lower portions, the unstriped fibres were found to predominate. The examina- 

 tions were made with a binocular microscope, which singularly increases the 

 beauty and distinctness of the appearances. 



