166 THE VITAL FUNCTIONS. 



anatomical details liave not as yet tended to eluci- 

 date in any degree the purposes to which they are 

 subservient in the process of digestion, I pass them 

 over as being foreign to the object of our present 

 inquiry.* 



It is essential to the perfect performance of di- 

 gestion, that every part of the food received into 

 the stomach should be acted upon by the gastric 

 juice ; for which purpose provision is made that 

 each portion shall, in its turn, be placed in contact 

 with the inner surface of that organ. Hence the 

 coats of the stomach are provided with muscular 

 fibres, passing, some in a longitudinal, and others 

 in a transverse, or circular direction ; while a third 

 set have an oblique, or even spiral course. f When 

 the greater number of these muscles act together, 

 they exert a considerable pressure upon the contents 

 of the stomach ; a pressure which, no doubt, tends 

 to assist the solvent action of the gastric juice. 

 When different portions act in succession, they 

 propel the food from one part to another, and thus 

 promote the mixture of every portion with the 

 gastric juice. We often find that the middle trans- 

 verse bands contract more strongly than the rest, 

 and continue contracted for a considerable time. 

 The object of this contraction, which divides the 

 stomach into two cavities, appears to be to separate 

 its contents into two portions, so that each may be 

 subjected to different processes; and, indeed, the 



* These structures have been examined with great care and mi- 

 nuteness by Sir Everard Home, who has given the results of his 

 inquiries in a series of papers, read from time to time to the Royal 

 Society, and published in their Transactions. 



t See Fig. 51, vol. i. p. 137, and its description, p. 138. 



