FOOD 95 



kingdom has to be drawn on. We have previously seen it 

 is quite capable of supplying the needs of the body, as the 

 vegetable contains the same constituents as those found in 

 the animal. 



When animal or vegetable proteid is digested it under- 

 goes a change in the stomach into peptone, while in 

 the bowels the peptone breaks up into certain amides, 

 known as leucin and tyrosin, thus carrying the stage of 

 proteid disintegration a step further. In the liver the 

 leucin is converted into urea which completes the final 

 breaking up of proteid. Urea is distinguished from proteid 

 in being a remarkably simple substance. As might be 

 expected, the different proteids do not all yield the same 

 amount of decomposition products in the process of diges- 

 tion. 



In the plant amides may also be found especially at an 

 early stage of its growth. 



Young growing clover, lucerne, and grass, contain a good 

 deal of amides ; as the plant approaches maturity they 

 become less in amount. 



The amides contain nitrogen, but not having the feeding 

 value of proteid, it is necessary to know how much of the 

 total nitrogen found in a plant is albuminous, and how 

 much amide. 



We have mentioned that in the animal body the amides 

 result from the breaking up of proteid ; in the vegetable, 

 on the other hand, there is evidence to show that it may be 

 part of the process of proteid construction. 



Animals have been fed with vegetable amides, and 

 experiments show that by becoming decomposed in the 

 body they economise the body proteid, so that if they can- 

 not replace proteid in a diet they are not entirely without 

 value. In the body these vegetable amides yield urea. 



In spite of these considerations, it is desirable in the 

 present state of our knowledge to regard amides as of very 

 little nutritive value in a diet. 



Here is a table* showing the proportion of albu- 

 * ' Farm Foods,' Wolff. 



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