22 THE PROTEIN ELEMENT IN NUTRITION 



organs and tissues. Instances of these are met with in the 

 group of autolytic enzymes, which are present in the different 

 tissues, and which split proteins into amino-bodies and nitro- 

 genous bases ; other examples are guanase of the thymus, 

 adrenals, and pancreas, which converts guanine to xanthine ; 

 adenase of the spleen, pancreas, and liver, which converts adenine 

 to hypoxanthine ; catalase found in many tissues, and which 

 decomposes peroxides this has been looked on as the reason 

 why oxidation takes place only in certain tissues, and not in 

 others where it is not required, as, for instance, in the blood. 

 The extension of the conception of the work of enzymes to all 

 phases of metabolic activity has greatly enlarged the outlook, 

 and has brought within measurable bounds the time when it will 

 be possible to explain the causes upon which the chemical 

 activities of the body depend. 



REFERENCES 



The following works of reference, monographs, and original papers have 

 been consulted and freely made use of in the preparation of the foregoing 

 introduction. 



VERWORN : General Physiology. London, 1899. 



LEATHES : Problems in Animal Metabolism. London, 1906. 



HILL : Recent Advances in Physiology and Bio -Chemistry. London, 1906. 



HILL : Further Advances in Physiology. London, 1909. 



CHITTENDEN : The Nutrition of Man. London, 1907. 



SUTHERLAND : A System of Diets and Dietetics. London, 1908. 



SCHAFER : Textbook of Physiology. London, 1898. 



V. NOORDEN : The Physiology of Metabolism. London, 1907. 



CATHCART : Protein Metabolism : Journal of Physiology, vol. xxxix., 1909. 



MELLANBY : Creatine and Creatinine. Journal of Physiology, vol. xxxvi.. 



1908. 

 LEVENE AND KRISTELLER : Factors regulating the Creatinine Output in 



Man. The American Journal of Physiology, vol. xxiv., 1909. 

 SHAFFER : The Excretion of Creatinine and Creatine in Health and Disease. 



The American Journal of Physiology, vol. xxiii., 1908. 

 SCHRYVER : Studies in the Chemical Dynamics of Animal Nutrition. The 



Bio-Chemical Journal, vol. i., 1906. 



PLIMMER : The Chemical Constitution of the Proteins, parti. London. 

 KRAUSE AND CRAMER : Proceedings of the Pyhsiological Society, May, 1912. 



