130 OF FOOD, AND THE DIGESTIVE PROCESS. 



of the process, the propulsion of the food down the oesophagus, then com- 

 mences. This is accomplished, in the upper part, by means of the constric- 

 tors of the pharynx ; and in the lower, by the muscular coat of the oesoph- 

 agus itself, which has been shown by Gillette 1 to be composed in its upper 

 part of striated muscular tissue alone, in its middle part of exclusively un- 

 striated muscular tissue, and near the cardiac orifice of the stomach of a 

 mixture of striated and unstriated tissue. When the morsels are small, and 

 are mixed with much fluid, the undulating movements from above down- 

 wards succeed each other very rapidly, as may be well observed in Horses 

 whilst drinking; large morsels, however, are frequently some time in mak- 

 ing their way down. Each portion of food and drink is included in the 

 contractile walls, which are closely applied to it during the whole of its 

 transit. The gurgling sound which is observed when drink is poured down 

 the throat of a person in urticulo mortis, is due to the want of this contrac- 

 tion. The whole of the third stage is completely involuntary. In order 

 to ascertain the parts implicated in the deglutition of liquids, Dr. Moura 

 employed the laryngoscope after ink had been swallowed, and found that 

 the parts tinted were the whole internal surface of the mouth, the velum pa- 

 lati, uvula, pillars of the fauces, anterior surface of the epiglottis, and the 

 pharynx generally, with the posterior surfaces of the cricoid and aryteuoid car- 

 tilages. On the contrary, the parts that preserved their natural color were 

 the interior of the larynx to within a very short distance of the free edge of 

 the epiglottis and the anterior portion of the lateral grooves of the fauces. 

 At the point where the oesophagus enters the stomach, the " cardiac orifice" 

 of the latter, there is a sort of sphincter, which is usually closed, but which 

 opens when sufficient pressure is made on it by accumulated food, closing 

 again, when this has passed, so as to retain it in the stomach. 



88. The purely automatic nature of the act of Deglutition is shown by the 

 fact, that no attempt on our part will succeed in performing it really vohui- 

 turUy. In order to excite it, we must apply some stimulus to the fauces. A 

 very small particle of solid matter, or a little fluid (saliva, for instance), or 

 the contact of the back of the tongue itself, will be sufficient; but without 

 either of these, we cannot xivallow at will. Nor can we restrain the tendency, 

 when it is thus excited by a stimulus; every one knows how irresistible it is, 

 when the fauces are touched in any unusual manner; and it is equally be- 

 yond the direct control of the will, in the ordinary process of eating, vol- 

 untary as we commonly regard this. Moreover, this action is performed, 

 like that of respiration, when the power of the will is suspended, as in pro- 

 found sleep, or in apoplexy affecting only the brain ; and it does not seem to 

 be at all affected by the entire removal of the brain, in an animal that can 

 sustain the shock of the operation; being readily excitable, on stimulating 

 the fauces, so long as the nervous structure retains its functions. This was 

 experimentally proved by Dr. M. Hall; and it harmonizes with the natural 

 experiment sometimes brought under our notice in the case of an unenceph- 



the second stage than it was described to he by Dzondi. He li;ul an opportunity of ob- 

 serving tin-in in ii woman, the left side of whose face had been removed by an oper- 

 ation. When the patient drank, the soft palate raised itself above the horizonal line, 

 as soon as the glass was approximated to her lips. It remained in this position whilst 

 the fluid was being sucked in ; but as soon as swallowing commenced it very suddenly 

 descended, so as to press the fluid into the oesophagus. It then again elevated itself 

 with even greater tension, and again descended. In swallowing solid food the same 

 sudden ascent and descent of the velum upon the deglutition of each morsel was 

 observable. 



J Gillette, Journ. de 1'Anatomie, 1872, p. (!17. See also for the Histology of the 

 Alimentary Canal, Klein and Verson in Strieker's Manual of Histology, Syd. Soc. 

 Transl., vol. i. 



