M.—AGRICULTURE 257 
‘In a series of lectures on the amino-acids, proteins and the proteolytic 
enzymes recently delivered in this country, Prof. Max Bergmann of 
Dresden describes the recent advances which have been made in our 
knowledge of the amino-acids and the polypeptides, as well as of the 
changes brought about by the enzymes which attack them. He shows 
that for more than thirty years chemists have been endeavouring to 
discover suitable methods for the synthesis of peptides containing the 
more complex amino-acids, but that only recently has a general method 
been developed. It is generally assumed that in the proteins the amino- 
acids are linked together by condensation of the carboxyl group of one 
amino-acid with the amino group of the next, a molecule of water being 
eliminated and an amide or peptide linkage formed ; the ordinary protein 
molecule is supposed to consist of a large number of such linkages. 
Bergmann points out that the outstanding problem of modern protein 
chemistry is to determine the effect of combination in peptide linkage on 
the different amino-acids, and; secondly, how the nature of the peptide 
linkage itself is influenced by the character of the amino-acids which take 
part in its formation. 
Investigations along these lines, while yet in an elementary stage, have 
thrown much light on many of the biological processes, e.g. the trans- 
formation of an amino-acid to a fatty acid, the biological degradation of an 
amino-acid to a keto-acid, and, conversely, the biological synthesis of 
creatine and many other reactions of the highest importance. Willstatter, 
Waldschmidt-Leitz and Bergmann and his fellow-workers have also devoted 
much time to the action of the enzymes which attack proteins and have 
made significant advances along this line of work. Summing up, Berg- 
mann states: ‘ The key to present day and future protein chemistry lies 
_ in the development of new synthetic methods, in the action of enzymes on 
proteins, and on an extension of the knowledge of protein metabolism 
both in normal and pathological cases.’ 
Similar advances in our knowledge of the structure of the carbohydrates 
have also been made. The work of Purdie and Irvine at St. Andrews 
and of Haworth and his school at Birmingham, of Staudinger, Zechmister 
and Mark in Germany and of other workers in the United States has been 
particularly important in elucidating the structure of these complex 
bodies. 
The structure of the simple sugars and of the di-saccharides has now 
been more or less worked out. The introduction of the six atom ring 
formula and the greatly increased use of stereo-chemical methods of 
exhibiting differences in structure have been important factors in the 
developments which have been made. 
- More recently, the constitution of the polysaccharides has been engaging 
much attention and speculation, and notable advances fall to be recorded 
both by chemical and by X-ray methods of investigation. ‘The adoption 
of Haworth’s hexagon formula for glucose has led to new interpretations of 
the experimental evidence bearing on the constitution of these substances. 
It has been shown by Haworth and his co-workers that the constitution 
assigned to cellulose rests ultimately on the constitution assigned to the 
di-saccharide cellobiose and the mutual linking of -glucopyranose 
K 
