416 THE ENZYMES OF THE INTESTINAL JUICE, [BOOK II. 



We may assume that, in addition to its diastatic enzyme, the pancreas 

 contains a trace of another ferment, capable of splitting-up maltose, 

 though the quantity of this ferment is altogether insufficient to 

 effect the complete conversion. Whilst the observations of Sheridan 

 Lea 1 throw some doubt on the existence of the latter enzyme 

 in the pancreas, the researches of Brown and Heron have, however, 

 led to the interesting discovery that the mucous membrane of 

 the small intestine (doubtless also, though perhaps less, the intestinal 

 juice) possesses, in an intense degree, the power of converting 

 maltose into grape sugar. The activity of the mucous membrane of 

 the small intestine in this respect is said to be much greater as we 

 approach its lower end, the maximum activity being possessed by 

 those parts of the jejunum and ileum in which Peyer's patches are 

 situated. 



The part played by the intestinal mucous membrane in reference 

 to the digestion of starches is thus seen to be complementary of that 

 exerted by the diastatic ferments of the saliva and the pancreatic 

 juice. Under the influence of these, the starch of the food is resolved 

 into dextrines and maltose, the amount of the latter rapidly amounting 

 to 80 per cent, of the starch digested. When digested with the intes- 

 tinal mucous membrane, this maltose is rapidly and completely 

 converted into grape sugar. The inversion of cane sugar by the 

 inverting ferment is, on the other hand, a process which proceeds 

 somewhat slowly, and which, as was previously stated, comes to a 

 standstill (in experiments in vitro) after the conversion has affected 

 25 per cent, of the saccharose present. The conversion of maltose 

 into grape sugar takes place rapidly and is a continuous process, 

 resembling in this respect the action of dilute sulphuric acid, which, 

 with the aid of heat, can effect the complete inversion of cane-sugar. 



The action of The intestinal juice possesses no special enzyme 

 the intestinal hi h actg f t When i ntes tinal juice is shaken 



juice on fats. -i * . j. >* 



with a neutral fat containing no trace of free acid, no 



permanent emulsion results. When however, as is always the case 

 after the action of the pancreatic juice upon the neutral fats, a trace 

 of free acid is present, the intestinal juice forms a durable emulsion 

 with fats. This property depends upon the sodium carbonate which 

 the juice contains, and which, as was pointed out, amounts on an 

 average to 0*5 per cent. In reference to its action on fats, indeed, 

 the intestinal juice has been supposed to act as a dilute solution of 

 sodium carbonate, and Bunge has argued strongly in favour of the 

 view that the chief function of the juice is to aid in the emul- 

 sionising of fats and thus promoting their subsequent absorption. 

 But such a view appears to the Author a very one-sided one, as the 

 presence of an alkaline fluid on the surface of the intestinal mucous 

 membrane would further not only the absorption of fat but also the 



1 Sheridan Lea, 'A Comparative Study of Artificial and Natural Digestion,' Journ. 

 ofPhys. Vol. xi. (1890), p. 227. 



