DIGESTION. 81 



" To determine the time requisite for digestion is evidently im- 

 possible, if we consider how it must vary according to the qua- 

 lity and quantity of the ingesta, the strength of the digestive 

 powers, and the more or less complete previous mastication. 



" During health, the stomach does not transmit the digestible 

 parts of the food before they are converted into a pulp. The 

 difference of food must therefore evidently cause a difference in 

 the period necessary for digestion/ It may, however, be stated 

 generally, that the chyme gradually passes the pylorus in be- 

 tween three and six hours after our meals." 



" The pylorus s is an annular fold, consisting, not like the other 

 rugae of the stomach, of merely the villous, but also of fibres 

 derived from the nervous and muscular, coats. All these, united, 

 form a conoidal opening at the termination of the stomach, pro- 

 jecting into the duodenum, as the uterus does into the vagina, 

 and, in a manner, embraced by it." 



The digestive process does not go on equally through the 

 whole mass of food, but takes place chiefly where this is in con- 

 tact with the stomach, and proceeds gradually from the surface to 

 the centre of the mass ; so that the food at the centre is entirely 

 different in appearance from that at the surface, and, as soon as a 

 portion is reduced to a homogeneous consistence, it passes into 

 the duodenum without waiting till the same change has pervaded 

 the whole. 1 



Dr. Prout considers the solution of the food to be a common che- 

 mical process, and to depend principally upon the combination of 

 water with the alimentary substance by means of the gastric juice. 

 He has shown that this part of the functions of the stomach is quite 

 distinct, and may exist or be absent independently of the assimi- 

 lating process. Thus, in some forms of dyspepsia, the solvent powers 

 of the stomach are almost entirely suspended, so that the patient, 

 though he may be able to assimilate pulpy matters, is quite unable 

 to digest any thing solid ; while in diabetes, the solvent power of 



r " Consult J. Walaeus, De motu Chyli, p. 534. LB. 1651. 8vo." 



s " H. Palm. Leveling, 'Dissert, sistens Pylorum, $c. Argent. 1764. 4to. 

 Reprinted in Sandifort's Thes. vol. iii." 



1 Dr. Prout, in The Annals of Medicine and Surgery, Lond. 1817., also in 

 Thomson's Annals of Philosophy, 1819. 



Dr. Wilson Philip, An Experimental Inquiry into the Laws of the Vital Func- 

 tions, $c. 1826. p. 121. sqq. 3d edit. Dr. Philip published subsequently to 

 Dr. Prout's first paper. . r 



G 3 



