Chap. 3 i.] Proofs ofDigefiion. 323 



fore an argument might be brought* that the abfor- 

 bents of the ftomach would refufe what the abforbents 

 of the jejunum would readily take up. But it muft 

 be confidered thar the milk is inftantly coagulated in 

 the flomach, and not in the jejunum, which coagula- 

 tion will perfectly prevent it from being abforbed 3 but 

 all thofe fubftances which are not changed by the 

 coagulating juice of the ftomach will be, and are 

 equally taken up by the lymphatics in the ftomach 

 and lafteals. There is, therefore, a converfion of the 

 food in the ftomachr into a new fubftance, whofe pro- 

 perties are at prefent unknown, which new fubftance is 

 the only one which can be converted into chyle in the 

 duodenum and jejunum, exactly as we may form fari- 

 naceous matter, mucilage, and native vegetable acid into 

 wine j but before they can poffibly be converted into 

 wine, they muft,firft be formed into fugar* So in a 

 fimilar manner farinaceous matter, gum, and white of 

 egg, are all capable of forming chyle ; but before 

 they are formed into chyle, they muft be converted 

 into a matter certainly not fugar, but a matter of a 

 particular fpecies in the ftomach, and by the ope- 

 ration of the ftomach, this particular fpccies of matter 

 is afterwards converted into chyle in the duodenum and 

 jejunum. 



Dr. Young, of Edinburgh, found that an infufionof 

 the inner coat of the ftomach, which had been pre- 

 vioufly warned with water, and then with dilute folu- 

 tion of mild fixed vegetable alkali, fo that it was not 

 pofiible that any acid could have remained in it, coa- 

 gulated milk very readily. He found alfo that it had 

 the power of coagulating ferum, and other animal mu- 

 cilages. The coagulating power of this fubftance is 

 very great. Dr, Fordyce mentions that fix or feven 

 Y 2 grains 



