THE POTATO 527 



as the greater part occurs in the inedible skin in 

 the form of a wax-like body. 



"The protein bodies are rather scanty, as com- 

 pared with those of cereals and such vegetables 

 as peas and beans. Only about 60 per cent, of 

 the total amount present is true protein that 

 is, in a form which can be used for the building and 

 repair of body tissue. This means that a pound 

 of potatoes furnishes only about 1.3 per cent, or 

 0.2 of an ounce of true protein, and emphasizes the 

 statement already made that potatoes alone make 

 a very incomplete diet, as the proportion of ni- 

 trogenous material would be very small in a quan- 

 tity sufficient to supply the body with all the 

 energy-yielding material required. 



"These potato proteids have been studied by 

 the Connecticut Experiment Station and found 

 to consist of a form of globulin, for which the name 

 'tuberin' is suggested, and a proteose, part of 

 these nitrogenous constituents being dissolved in 

 the juice and part stored with the starch in the 

 cells, especially in the cortical layer. 



"The nonproteid forms of nitrogenous sub- 

 stances in the potato are asparagin and small 

 quantities of amido acids, occurring mostly in the 

 juice. If they have any food value it is indirect 

 and due to the fact that they protect the true pro- 

 teids from waste during digestion. It is possible 

 that they may aid digestion in some way or serve 

 a similar purpose. There is a larger proportion of 

 protein compounds, and especially of the more 

 soluble forms, in young potatoes than in old. 



"The most important mineral matters found in 

 potatoes are potash and phosphoric acid com- 

 pounds. There are several organic acids (as citric, 

 tartaric and succinic acid), which vary in tubers 



