SALIVA AND SALIVARY DIGESTION. 73 



between the taking out of drops from each of the three mix- 

 tures may be disregarded, if we work quickly. 



In order to obtain a better and clearer insight into the 

 progress of the process, select for each new test of the mix- 

 tures a new row of drops of the iodine solution on the plate. 

 This arrangement enables us even to recognize erythrodextrin, 

 if it is present in sufficient quantity, alongside of the starch. 

 In this case besides the blue color due to starch the red color 

 due to erythrodextrin will appear when the drops begin to 

 dry. Test the portions taken out later also for sugar; a very 

 small quantity is sufficient for this. 



V. ISOLATION OF THE PRODUCTS OF SALIVARY DIGESTION. 



Make 25 g. of starch into paste with one liter of water, 

 stirring constantly. After cooling to 40 (in order to deter- 

 mine the temperature, the thick paste must be well stirred, 

 as the distribution of the temperature in it is very unequal), 

 add 25 cc. of saliva, and stir thoroughly (it is advisable to use 

 saliva that has been collected the previous day, as its activity 

 appears to be greater). The paste very soon liquefies. As 

 soon as this has happened pour the paste into a cylinder and 

 digest for two and a half to three hours at 40. After this 

 time, as a rule, the starch will have disappeared, the solution 

 no longer gives the reaction for starch with iodine. An abso- 

 lutely exact statement of the time necessary cannot be made, 

 as the activity of the saliva is not always the same. If the 

 starch has not entirely disappeared, the digestion must be 

 continued. It is not advisable to carry the digestion to an 

 end in the dish originally used, since the formation of solid 

 masses of the paste on the side of the vessel is scarcely to be 

 .avoided, and these resist the digestive action of the saliva for 

 a long time. This again might lead to a false impression con- 

 cerning the progress of the digestion. After the digestion 

 is completed heat the solution on the water-bath, filter from 



