BIOCHEMISTRY 



205 



BIOCHEIMISTB.Y. By Prof. J. C. Drummond, D.Sc, University College, 

 London. 



Biological Value of Proteins. — The last number of the Bio- 

 chemical Journal (vol. xvi, No. 3) contains an outstanding 

 paper by Martin and Robinson (p. 407) on the minimum 

 nitrogen expenditure of man and the biological value of various 

 proteins for human nutrition. After a useful and concise 

 survey of the historical side of this subject the authors, who 

 state that they commenced the investigation light-heartedly 

 with the object of re-determining the relative values of certain 

 cereal proteins in human nutrition, point out the many diffi- 

 culties which they encountered in arriving at values which 

 could justifiably be compared. To determine the nitrogen 



minimum it is necessary to make a number of experiments 

 each extending over several days, for if rehance is placed on the 

 methods of Thomas {Arch. Physiol., 1909,219), who calculates the 

 minimum requirements from a very limited number of obser- 

 vations, it is necessary to assume that the value of any protein 

 for biological purposes remains uniform whatever the amount 

 taken. Such an assumption is apparently one for which there 

 is no justification. Thus the biological value of gelatin, if 

 calculated by any of Thomas's formulae, would therefore appear 

 quite appreciable when the intake was small, but almost zero 

 if the intake was very large. Yet Boruttau (Biochem. Zeit., 

 1 9 19, 94, 194) has actually made use of these formulae to 

 calculate the biological value of gelatin as being 58-2 per 

 cent. The authors make these points clearer by a useful 



14 



