No. 533] NUCLEUS AND CYTOPLASM IN HEREDITY 297 



side the pale of the well-known principles of constitution, 

 polymerization, stereometry and the like which are 

 known to obtain in simpler organic compounds such as 

 the "ring" compounds or aromatic series, and the 

 straight chain or aliphatic series. 



It is a familiar fact that the native proteins are read- 

 ily broken down through hydrolysis into simpler bodies 

 which still possess protein characteristics. We may in 

 fact either artificially or in normal digestion get a whole 

 series of stages ranging from complex native proteins 

 to simpler and simpler products. The sequence runs 

 approximately as follows: 

 Proteins. 



— Meta- or infra-proteins, 

 —Proteoses. 

 — Peptones. 



— Polypeptids (a relatively small 

 number of amino-acids 



Three fourths of the albumin molecule, for example, 

 may be made to yield members of the large group of 



Because of the great abundance of these bodies, and 

 because of their universal presence as degradation prod- 

 ucts of proteins, the conclusion was reached that the 

 protein molecule is essentially built up by a linking to- 

 gether of amino-acid molecules. This suggested the idea 

 that by bringing about such linkage it might be possible 

 to build up molecules of the protein type. To those who 

 are familiar with the recent developments of physiolog- 

 ical chemistry, the fact that the first steps toward this 

 end have already been accomplished is well known. 

 Some seven or eight of the amino-acids (leucin, tvrosin, 

 glycocoll, alanin, aspartic acid, phenvl-alanin, and 

 amido-valerianic acid) had already been produced 

 synthetically before Emil Fischer began his work. 

 Fischer and his pupils have synthesized over twenty 

 new members. But what is still more significant, they 



