TRANSACTIONS OF SECTION B. 461 
obtained from the moths were equivalent in amount to those from the 
worms minus those from the cocoons. To complete the story, it obviously 
remains to investigate the nature and quantity of the monoamino acids 
present in the proteins of the mulberry leaves which serve as food to 
the worms ; Professor Abderhalden’s further results will be awaited with 
interest. 
In comparing proteins it is not enough to establish the nature and 
amount of the structural units, but it is necessary further to study how 
the monoamino acids are coupled together to di- and poly-peptides. Any 
pair of amino acids can give rise to two isomeric dipeptides with different 
physiological properties. The dipeptide glycylalanine, for example, behaves 
quite differently towards digestive enzymes than does the isomeric alany]l- 
glycine. Presumably a food containing the former would be less easily 
assimilated than one yielding the latter complex. This part of the subject 
is as yet in its infancy but it may be expected to yield results of great 
significance. 
To sum up, when discussing the value of foods it is not enough to know 
merely the gross amount of nitrogen containing matter, but the nature and 
proportion of its constituent units must also be taken into account. The 
ideal diet should contain as great a variety of proteins as possible in order 
to provide a sufficient amount of all the required unity of constructive 
metabolism. 
(ii) Some Physiological Problems in Agriculture. 
By EH. J. Russewy, D.Sc. 
(iit) Economic Aspects of Cattle Feeding. 
By Professor J. Wiuson, M.A., B.Sc. 
