OF FOOD AND THE DIGESTIVE PROCESS. 



(e), in which alone the true digestive process takes place. Now, that the 

 condition of the food as to bulk and solidity is the circumstance which 

 determines the opening or closure of the lips of the groove, and which 

 consequently occasions its passage into the first and second stomachs, 

 or into the third and fourth, appears from the experiment of Flourens ; 

 who found that when the food, the first time of being swallowed, was 

 artificially reduced to a soft and pulpy condition, it passed for the most part 

 along the demi-canal into the third stomach, as if it had been ruminated, 

 only a small portion finding its way into the first and second stomachs. 

 How far the actions of this curious apparatus are dependent upon ner- 

 vous influence, or how far they are due to the exercise of the contrac- 

 tility of the muscular fibre, directly excited by the contact of the sub- 

 stances with the lining membrane of the tubes and cavities, has not 

 yet been clearly ascertained. 



458. The food, when introduced into the stomach, and submitted to 

 the solvent action of its secretions, is also subjected to a peculiar move- 

 ment, which is effected by the muscular walls of that organ. The pur- 

 pose of this motion is obviously to keep the contents of the stomach in 

 that state of constant agitation, which is most favourable to their 

 chemical solution ; and particularly to bring every portion of the ali- 

 mentary matter into contact with the walls of the stomach, so as to be 

 subjected to the action of the fluid, which is poured forth from them 

 during the digestive process. The movement is produced by the alter- 

 nate shortening and relaxation of the various fasciculi, which are dis- 

 posed in almost every direction throughout the muscular wall of the 

 stomach ; and it seems to produce a kind of revolution of the contents 

 of the stomach, sometimes in the direction of its length, and sometimes 

 transversely. Its result is well shown in the hair-balls, which are occa- 

 sionally found in the stomachs of animals, that have swallowed hair 

 from time to time through licking their skins ; the component hairs not 

 being pressed together confusedly, but being worked together in regular 

 directions, and so interwoven that they cannot be readily separated. 

 As digestion proceeds, the dissolved fluid escapes, little by little, through 

 the pyloric orifice, which closes itself firmly against the passage of 

 solid bodies ; and this motion continues until the stomach is completely 

 emptied ; when it ceases, until food is again introduced. The bulk of 

 the alimentary mass diminishes rapidly, as the solvent process is near 

 its completion ; and the separation of the fluid product or chyme is 

 aided by a peculiar action of the transverse fasciculi, which surround 

 the stomach at about four inches from its pyloric extremity. These 

 shorten in such a manner, as to produce a sort of hour-glass separation 

 between the portions of the stomach on either side of it ; and the fluid 

 solution, being received by the pyloric or smaller portion, is pumped 

 away through the pylorus ; whilst the solid matter yet undissolved is 

 retained in the larger division. 



459. The degree in which these movements are dependent upon the 

 nervous system, or are under its control or direction, has not yet been 

 clearly ascertained. Distinct movements may be excited in the stomach 

 of a Rabbit, if it be distended with food, by irritating the par vagum 

 soon after the death of the animal; these movements seem to commence 



