4lU DIGESTION. 



tannie acid ; acetic acid and solution of potassium ferrocyanide ; 

 platinum chloride; solution of iodine. No precipitate appears 

 in anv case, Imt the iodine produces a ^yellow color. 



\dd lead acetate, and to another quantity basic lead ace- 

 tate. In both cases a precipitate is formed after a time, and on 

 filtration it. is found that the filtrate is without action on starch, 

 the ptyalin having been carried down with the precipitate. 



4. Add liquor potass and cupric sulphate. No reduction of 

 the copper oxide occurs. 



** 85 Secretion of Saliva. The secretion of saliva goes 

 on very slowly or ceases entirely when the glands are not under 

 the influence of some stimulus. The stimulus may be either 

 mechanical, chemical, electrical, or mental. The student may 

 otimate tlu' effect of different stimuli by experiments on him- 

 self, thus: Swallow all the saliva contained in the mouth, so as 

 to empty it eompletely. At the end of two minutes spit out 

 the saliva which has collected iu the mouth into a small beaker 

 previously counterpoised (S * -!">) and weigh it. Again 

 empty the mouth, apply the stimulus and colled the saliva 

 for t \\ o minutes more, and weigh as before. I*y the comparison 

 of the two, the action of the stimulus may be judged of. The 

 -timulation are the following: 



1. M, <!,,,,< I. \\u\\ a pebble or glass stopper in the month, 

 and attempt to chew it. 



_'. < 'lifmi'-nf. Touch the tongue (1 ) with a crystal of tartaric 

 or citric acid, or ( '2 ) of sodium carbonate: (.'>), fill the mouth 

 with ether vapor, allowing it to pass back into the pharynx, 

 and retaining it for some time in the mouth. 



:;. I-'.lr, -tri>-<iL Touch the tongue and inside of the cheeks 

 with tin- electrodes of I hi IJois Keymnnd's induction coil. 



The effect which a stimulus applied to the mouth produces 

 in man. on the secretion from the parotid and submaxillary 

 glands, may be studied with greater precision by means of a 

 canula or syringe. If a syringe is used, its no/./le must end in 

 a funnel-shaped dilatation. This is applied to the papilla at 

 the orifice Of 'W barton's or Stenson's duets, and gentle traction 

 made upon the piston. A stimulus may be applied to the 

 mouth, and the rate at which the saliva Hows afterwards ob- 

 1. It is, however, more satisfactory t use a canula, which, 

 with a little practice, can be introduced into the ducts with 



*86. Mode of Collecting the Secretions of the Sali- 

 vary Glands unmixed in Man. Inm Ttinn /' a Cnnnfa 

 iiifn the Submaxillary Duct. Draw out a narrow glass tube to 

 a line point, and at the place where it seems small enough to 

 enter the orifice of the duct, notch it with a triangular tile, 

 break it off, round the edges at the border of a glass flame and 

 allow it to cool. To insert a canula thus prepared into his own 



