58 APPLIED PHYSIOLOGY 



In addition to these ferments, intestinal juice contains 

 a series which invert the various sucroses (cane-sugar, 

 lactose and maltose) into dextrose and laevulose, the 

 existence of which has long been known, and by means 

 of which it completes the work already begun by the 

 saliva and the pancreatic juice. 



The stimuli which lead to the production of normal 

 intestinal juice have not yet been clearly made out, 

 though here again secretin is believed to play a part. 

 Mechanical stimuli lead to the production of a very 

 watery secretion which has little or no digestive 

 power, and the object of which, apparently, is to wash 

 away the source of irritation. It is in this way, seem- 

 ingly, that solid indigestible substances, as well as some 

 purgatives, excite diarrhoea. 



Intestinal Movements. 



The intestine exhibits two forms of movement : (1) 

 Movements of rhythmical segmentation (which occur at 

 the rate of about seven per minute in man), the 

 object of which is to ensure thorough mixing of the 

 contents of the gut, but which have no translatory effect 

 (Fig. 17). These movements are most vigorous in hunger, 

 the small amount of material left in the intestine being 

 searched again and again for nutriment until it has all 

 been absorbed, just (to quote a German writer) as one 

 may peel an apple, eat it, and then nibble the peel. An 

 exaggeration of these movements in nervous subjects is 

 the cause of borborygmi, which, as is well known, 

 are most troublesome when the stomach is empty. 



