34 PROTOPLASMIC ACTION AND NERVOUS ACTION 



protoplasmic structures; in such a case a specific proto- 

 plasmic and ultimately a specific cellular structure 

 would be produced, corresponding to the specific constitu- 

 tion of the structure-forming compounds. 



The general nature of the relation between stereo- 

 chemical configuration and crystalline form is best 

 illustrated by Pasteur's classical investigations on the 

 tartrates. The characteristic spatial arrangement of the 

 atoms in the d-tartrate molecule is evidently what 

 determines the production of the specifically formed 

 asymmetric crystals of this compound. Similarly con- 

 stituted molecules have a tendency to segregate, hence 

 the dextro- and laevo-groups in the solution of the 

 racemic salt unite separately to form separate crystals. 

 The importance of such conditions in the chemical 

 processes of protoplasm is illustrated in the characteristic 

 relations existing between the stereo-configuration of 

 asymmetric compounds and their assimilability, ferment- 

 ability and physiological action. The possibilities of a 

 specificity based on stereo-chemical configuration are at 

 a maximum in compounds like proteins, built up of 

 chains of asymmetric amino-acids. As we have seen, 

 chemical specificity implies structural specificity in the 

 aggregate formed from such molecules. 



As is well known, the chief proofs of the chemical 

 specificity of closely related proteins are derived from 

 immunological and related phenomena. Antigenic prop- 

 erties are apparently confined to proteins, and this 

 peculiarity is of fundamental importance in relation to 

 the whole problem of the conditions of specific synthesis 

 in organisms. When a foreign protein is introduced into 

 the tissue-media of higher animals, one of its physiological 



