460 Ruyal Society. 



and ligatures placed at short intervals on the intestinal canal, from 

 the pylorus to the rectum. The contents of the stomach and each 

 portion of the intestinal canal included between the ligatures were 

 then carefully examined. This mode of examination sufficed to 

 determine the changes which occur in the food during normal diges- 

 tion ; but other questions as to the particular secretion or secretions 

 by which the changes observed were effected. 



The fluids poured into the alimentary canal are five in number, — 

 the saliva, gastric juice, bile, pancreatic juice, and finally, the intes- 

 tinal mucus. 



The influence of the saliva is easily determined, by chewing the 

 particular food subjected to experiment, and keeping the mixture at 

 about 98° Fahr. The combined action of the saliva and gastric 

 juice is seen in the contents of the stomach. To determine the 

 action of the bile, the common bile-duct was tied, and to ascertain 

 the action of the intestinal mucus, it was necessary to ligature the 

 bile and pancreatic ducts. If the digestion of the substance is not 

 effected in the stomach, it is evident that it cannot be attributed to 

 the saliva or gastric juice; if the digestion is still effected in the 

 intestinal canal after ligature of the bile-duct, it cannot be attributed 

 to the action of the saliva, gastric juice or bile ; if it still go on 

 after ligature of the bile and pancreatic ducts, the digestive power 

 must of necessity be referred to the action of the intestinal mucus, 

 provided no change has previously taken place in the stomach ; but 

 if the food passes unchanged after cutting off the supply of bile and 

 pancreatic juice, but proceeds after ligature of the bile-duct alone, 

 the act of digestion must be referred to the pancreatic juice. 



The author first briefly describes the structure of the starches and 

 starch-containing vegetables employed in his experiments ; then the 

 changes produced by cooking, and finally enters on a minute descrip- 

 tion of the changes observed in the experiments he performed on 

 normal digestion, and after cutting off the supply of bile and pan- 

 creatic juice. 



The correct appreciation of the structure of the starch-granule is 

 of considerable importance in relation to these investigations, and 

 the author believes that he has been able to afford a satisfactory 

 solution of this vexed question. The changes observed during the 

 digestion of starch favour the original opinion of Leuwenhoeck, that 

 the starch-granule consists essentially of an investing membrane or 

 cell-wall, enclosing an amorphous matter, the true starch, which 

 strikes an intense blue colour with iodine ; and these changes also 

 support the opinion of Professor Quekett, that the concentric circles 

 seen on the starch-granules of many plants are simple foldings of 

 the investing membrane, leaving it still doubtful, however, whether 

 these concentric circles are not in the starches of some plants com- 

 posed of linear series of dotted elevations or depressions of the in- 

 vesting membrane. 



By these experiments it was determined that the concentric circles 

 remain after the whole of the starch matter, colourable by iodine, 

 was removed, and that even then the characteristic cross and colours 



