1913^ Chemistry of Diet 181 



these complicated processes associated with the intri- 

 cate iDi'otein molecules are beginning to clear up. It has 

 been the good fortune of Dr. Osborne, whom I mentioned above, 

 to play a leading part in the solution of these problems. Quite 

 within this decade the protein molecule has begun to yield its 

 great store of secrets and we are now in possession of practically 

 all the decomposition products of the most familiar proteins 

 and the gross molecular composition of the most important con- 

 stituent of the dietary is quite well known. The average pro- 

 tein has a molecular weight of approximately 2000, and consists 

 of practically 24 distinct chemical substances, linked together 

 to form the complete protein. The simplest protein molecule 

 consists of about 15 distinct and diiferent amino acids and 

 about three more basic substances, and when the protein ma- 

 terial is such a one as nucleoprotein, it contains phosphorus 

 in that complicated organic body, nucleic acid. Then the chem- 

 istry of it becomes even more comj^licated, though the compo- 

 sition of the nucleic acids also is quite well understood today. 



It is through just such careful feeding experiments as those 

 conductor by Osborne and Mendel today that these questions of 

 specificity of the diet are being answered. Such feedings for 

 long periods on a single protein substance, while all other con- 

 stituents of the diet are satisfied, has shown for long time that 

 w^hen that protein substance is gelatine, wheat gliadin, zein 

 from the maize, etc., that the animal cannot live beyond a rea- 

 sonable wasting period. Why ? Because those proteins do not 

 contain all the elements necessary for tissue synthesis. Gelatin 

 or wheat gliadin have little or no tryptophane, little glycocoll, 

 and are short in other respects of certain food groups which the 

 body must get from the alimentation to manufacture blood 

 serum-albumin, muscle-myosin, hematin, haemoglobin and the 

 like tissues of the body. It is simply a problem of chemical con- 

 struction. The building materials must be supplied. If you 

 wish to build a brick house you buy brick, lime, sand and water. 

 Therefore, if you w^ish to build a human body, you must sup- 

 ply the chemical building stones or ''Bausteine." 



In regard to the proteins, they are apparently not strictly spe- 



