THE BIO-CHEMISTRY OF ANIMALS 



AND PLANTS 



A COMPARATIVE STUDY.— I 



By O. ROSENHEIM, Ph.D. 



Lecturer on C/temical Physiology, King's College, London 



Chemistry, at one time intimately connected with biology, 

 drifted away from this science during the past century, mainly 

 owing to the apparent exhaustion of its methods in their useful 

 application to biological problems. Meanwhile the edifice of 

 chemistry has been perfected to such a degree that chemists 

 are again able to attack biological questions with the help of 

 new experimental methods. In consequence it is being more 

 and more recognised that the sharp separation of animal and 

 vegetable biology has only been an artificial one and does not 

 really exist. Formerly it was held that the plant alone possessed 

 the power of building up organic substances, i.e. of synthesis. 

 The animal body, it was thought, had mainly the function of 

 breaking down the substances supplied to it by the plant. The 

 first synthesis taking place in the animal body was demonstrated 

 by the classical work of Wohler in 1824, when he showed that 

 benzoic acid in its passage through the body was linked up 

 to glycine and excreted as hippuric acid. Many similar 

 instances of synthetical processes occurring in the animal 

 body have since been found (to mention only the latest one, 

 i.e. the synthesis of proteins from amino acids), and although 

 no doubt the synthetical power of the animal organism is less 

 than that of the plant, we know now many biological processes 

 which are common to both. 



The purpose of the following pages is to discuss in outline 

 some of the progress made in this " Grenzgebiet " (borderland) 

 of bio-chemistry. 



The Nitrogenous Cycle 



If we consider first the nitrogenous substances which play 



such an important role in the animal organism, it is evident that 



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