Soluble ferments Digestion. 231 



If the diastase were associated with yeast in the above action on the 

 starch, the dextrine molecule would become glucose also, and all of them 

 would by the action of the yeast become alcohol and carbonic dioxide. 



The diastasic ferment in the pancreatic juice is very powerful, being 

 practically instantaneous. 



The presence of the ferment in germinating seeds has been mentioned. 

 It shows itself IE the spring in the potato, dissolving the starch. The 

 ferment follows the formation of glycogen in the liver as mentioned 

 above. 



But there is a curious exception in the case of animals that undergo 

 metamorphoses. The larva of the house fly is stuffed full of starch 

 or glycogen, which is not turned to sugar while the fly remains in that 

 state. But when the fly passes from the larval to the chrysalis stage 

 the ferment appears and the glycogen is dissolved and used up in the 

 construction of new tissues. According to Bernard, something like this 

 happens in the foatal life of mammals. A time arrives wh,en deposits 

 of glycogen, which have previously been made, are required to promote 

 rapid growth of certain parts, when this material is suddenly converted 

 into sugar and used up. 



The frog, something like the fly and the plant, appears to be influ- 

 enced by the season in the secretion or activity of his diastase. This 

 ferment exists in the blood in its veins during the spring and summer, 

 so that if dextrine be injected into the veins it is turned to sugar ; but 

 if it be injected in winter, the dextrine will pass through the veins and 

 be carried off in the urine without change. 



The diastase has been found in the digestive tube of the silk worm by 

 Balbini. In short, it is found in all animals and plants that use 

 starchy substances for food ; if it were not, such substances would not 

 be food at all. 



It thus appears that the vegetative economy of the human and other 

 animal organisms includes as a necessary part of their machinery a 

 number of vegetable ferments or zymases ; the counterparts of which 

 are to be found in various plants. Furthermore, the cells of many of the 

 tissues themselves are able to disintegrate appropriate food stuff and 

 select out of it what they need. Thus if meat be introduced into a 

 subcutaneous wound it will become digested as in the stomach. But 

 starch or cane sugar in the same locality would remain unchanged and 

 pass through the blood and be eliminated as an excretion. The soluble 

 ferments of vegetables become necessary to them because the sort of 

 food prepared for them by the action of sunlight upon chlorophyl is the 

 insoluble unassimilable starch. Furthermore, it is plain that a sub- 

 stance which could not be made soluble when wanted by the plant 

 would not answer for its food in a climate where the active growth is - 



