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A MANUAL OF PHYSIOLOGY 



add a drop of the mixture in the test-tube to one of the drops of 

 iodine at intervals as digestion goes on. At first only the blue colour 

 given by starch will be seen ; a little later a violet colour, due to the 

 presence of erythrodextrin in addition to some unaltered starch. A 

 little later the colour will be reddish, the starch having disappeared, 

 and the erythrodextrin reaction being no longer obscured. Later still 

 no colour reaction will be obtained, the erythrodextrin having under- 

 gone further changes, and only sugar (maltose, isomaltose, and 

 perhaps a trace of dextrose) and achroodextrin a kind of dextrin 

 "which gives no colour with iodine being present. 



(g) Put a little distilled water in a porcelain capsule, and bring the 

 water to the boil. Now put into the mouth some boiled starch 

 paste, and move it about as in mastication. After half a minute spit 



Submaxillary Carotid 

 Gland. Artery. 



Chorda 

 Tympani. 



Digastric 

 Muscle (cut). 



.(glossal Mylo-hyotid 

 Jerve. Muscle (cut). 



Lingual Wharton's 

 Nerve. Duct. 



FIG. 113. DISSECTION FOR STIMULATION OF CHORDA TYMPANI 

 (AFTER BERNARD). 



the starch out into the boiling water. Divide the water into two 

 portions. Test one for sugar, and the other for starch. Repeat the 

 experiment, but keep the starch two minutes in the mouth. Report 

 the result. 



(ti) Starch solution to which saliva has been added is placed in a 

 dialyser tube of parchment paper for twenty-four hours. At the end 

 of that time the dialysate (the surrounding water) should be tested 

 for sugar and for starch. Sugar will probably be found, but no 

 starch. If no reaction for sugar is obtained, the dialysate should be 

 concentrated on the water-bath, and again tested. 



2. Stimulation of the Chorda Tympani. (i) Having previously 

 studied the anatomy of the mouth and submaxillary region in the 

 dog by dissecting a dead animal (Fig. 113), put a good-sized dog 



