LETTERS TO BROTHER JOHN. 133 



chyme, floats away after it to the pylorus, that is, 

 the lower extremity of the stomach. Thus, layer 

 after layer, the whole mass eventually becomes 

 changed from the nature of food into chyme ; 

 gastric juice, during the whole time this change is 

 going on, being poured out from the internal sur- 

 face of the stomach upon fresh surfaces of the ali- 

 mentary mass. The whole quantity is usually con- 

 verted into chyme in about four hours. 



Now mark ! Whatever has been the nature and 

 kind of the food which you have eaten, however 

 heterogeneous the several viands may be, they 

 must all be reduced to this unique homoge- 

 neous semi-fluid, called chyme they must all lose 

 their own several natures, and take upon themselves 

 the one sole nature of chyme, and so become 

 chyme itself before they can leave the stomach, 

 and enter the bowels, in order there to undergo 

 the next necessary change. 



Now, if you have eaten any matters at your meal 

 which are what is called "difficult of digestion," that 

 is, which are not easily reduced to chyme by the 

 action of the gastric juice ; when these matters 

 become exposed to the action of the gastric juice, 

 they will necessarily require to be so exposed for a 

 longer time than is natural, because of the difficulty 



