6 



3. Maintenance of Optical Purity by the So-Called 



''Stereo-autonomic Substances" 43 



4. Procedures Used by Nature for Maintaining Opti- 



cal Puritv and Establishing a ''Fixed Internal 

 Milieu" ■ 45 



5. Biological Advantages of Optical Purity 51 



6. The Origin of the Asymmetry of Protoplasm. 52 



7. General Survey of the Problem of the Origin and 



Maintenance of Optical Asymmetry 53 



CHAPTER III 



HEREDITY AND THE INFLUENCE OF ENVIRONMENTAL 



FACTORS ON THE OPTICAL ACTIVITY OF 



BIOLOGICAL MATERIAL 



1. The Impossibility of Inverting the Optical Prop- 



erties of the Primary Constituents of Proto- 

 plasm 59 



2. The Impossibility of Modifying Protoplasm so as 



to Cause it to Invert the Optical Properties of 

 the Products of its Metabolism 61 



3. Mechanisms Controlling the Production of a Given 



Optical Isomer 67 



a. Production of Dissyinmetrir Substances from 



Symmetric Phenyl-Glyoxal 67 



&. Production of Optical Isomers by Esterases 68 



c. Production of Optical Isomers bv Oi)tically Active 



Alkaloid Catalysts ' *.... 68 



d. Production of a Given Optical Isomer by a Chemi- 



cal Alteration of the Catalyst .'. 69 



e. Control of the Production of Optical Isomers by 



Intermediate "Pathways'' 70 



/. Control of the Production of Optical Isomers by 



an Inversion of the Waldeu Tyije 73 



CHAPTER IV 



ON THE RELATION BETWEEN THE INVERSION OF 



SPIRALLY TWISTED ORGANISMS AND THE 



MOLECULAR INVERSION OF THEIR 



PROTOPLASMIC CONSTITUENTS 



1. Morphological Dissymmetry and Morphological In- 

 version - 79 



