794 PHYSIOLOGY 



cent, solution of boiled starch, within a few seconds the solution clears, 

 and in half a minute, on the addition of iodine, a red colour is obtained, 

 showing the presence of erythrodextrin. At the end of a few minutes 

 no colour is obtained with iodine, and the solution contains maltose. 

 The stages in the hydrolysis of starch brought about with pancreatic 

 juice are exactly similar to those effected by ptyalin. If the juice be 

 neutralised, it is found that the process of hydrolysis goes on to the 

 formation of dextrose or glucose. This further conversion is due 

 to the presence in the juice of a second ferment maltase which 

 converts the disaccharide maltose into the monosaccharide glucose. 

 The juice in the gut is therefore able to effect the further digestion 

 of the products of salivary digestion. On the other disaccharides 

 pancreatic juice is without effect. It contains no invertase, nor 

 does it, in spite of certain statements to the contrary, ever contain 

 lactase. It has therefore no effect on either cane sugar or milk sugar. 



THE ACTION OF PANCREATIC JUICE ON FATS 

 Fresh pancreatic juice contains a strong lipase or fat- splitting 

 ferment, by means of which, in the presence of water, neutral fats, 

 e.g. the triglycerides of palmitic, stearic, and oleic acids, are broken 

 up into glycerin and the corresponding fatty acids. This ferment 

 is active either in alkaline, neutral, or very slightly acid reaction. 

 If the reaction be alkaline the fatty acids produced by the lipolysis 

 combine with the alkali present with the formation of soaps. The 

 ferment may be obtained from extracts of the fresh gland, but is 

 rapidly destroyed if active trypsin be present. It is also contained 

 in some of the dried commercial preparations of trypsin. It is 

 apparently insoluble in distilled water, and is therefore found in 

 the residue after extracting these commercial preparations with 

 water. It is easily soluble in glycerin. The velocity with which 

 lipolysis occurs is much increased (four to five times) by the addition 

 of bile. This adjuvant action of bile is not destroyed by boiling, 

 and is due entirely to the bile salts. These act in two ways. In the 

 first place, by their physical qualities they diminish the surface tension 

 between water and oil, so enabling a closer contact to be effected 

 between the watery solution contained in the juice and the oil which is 

 presented to it. Moreover they may aid in the solution of the ferment 

 itself. In the second place, bile salts have a solvent action on soaps 

 as well as on fatty acids in slightly acid medium. Bile may be regarded 

 therefore as a favourable excipient or medium for the interaction of 

 the lipase and the neutral fats. The lipase of pancreatic juice will 

 also hydrolyse the esters of the fatty acids, such as ethyl butyrate 

 or monobutyrin. On the phosphorised fats or phosphatides, such as 

 lecithin, its action is still a subject of doubt. According to certain 



