PRESIDENTIAL ADDRESS. 421 
peptides, of natural terpenes and camphor, of indigo and rubber, are well-known 
achievements, while natural processes, in which enzyme action plays a part, are 
yielding their closely guarded secrets to the persistent inquiry of Armstrong and 
his collaborators, who are probing the relationship between enzyme: and sub- 
strate which Emil Fischer pictured as that of lock and key. Further, there 
is that large field of work which includes not only the Walden inversion but 
new problems of asymmetry, with which the names of Frankland, Pope, Werner, 
and others are associated; while Barlow and Pope’s conception of the relation 
of valency to atomic volume, by correlating crystalline structure with the com- 
position, constitution, and configuration of carbon compounds, has given a new 
interest to the study of crystallography. 
Nor is progress less rapid in that other important branch of chemistry—the 
unravelling of the structure of natural products. The constitution of rubber is 
approximately known; most of the alkaloids have been explored with a greater 
or less degree of completeness; and now the study of starch,*’ chlorophyll, and 
hematin (the non-proteid constituent of hemoglobin) ** has been taken up afresh 
during the last three years, with results which, in the case of the two latter, 
eclipse in importance and interest all that was previously known. In whatever 
direction we may look, there is the same evidence that we can take to pieces 
the most complicated structure which nature has devised, and by the aid of 
valency conceptions can fit the pieces into a formula which is an epitome of 
the chemical activities of the molecule. Again, in many cases the resources 
of our laboratories enable us to build up the structure thus displayed, and to 
establish the identity of nature’s product and our own. Nevertheless, the fact 
remains that all these syntheses leave untouched and unexplained the profound 
difference between the conditions we find necessary to achieve our purpose and 
those by which the plant or animal carries on its work in presence of water and 
at a temperature differing only slightly from the normal. It is, of course, a well- 
known fact that an enzyme under the appropriate conditions can bring about the 
same chemical transformation of a substrate as is effected by the living cell from 
which it can be separated; but our knowledge of these complex, ill-defined, 
nitrogenous organic compounds is relatively very meagre; they are difficult to 
purify, and their composition—apart from any question of structure—is largely 
unknown. Yet because Wohler chanced to discover that urea can be produced 
synthetically from an inorganic source the conclusion is not infrequently drawn 
that all chemical changes in living substance are brought about by ordinary 
chemical forces.*’ Probably everyone present will concur in that view, but the 
assent, if given, can hardly arise from a consideration of the facts, of which there 
is no great store. Where so little is known accurately, chemistry is not on very 
safe ground if she infer the rest. What common basis of comparison exists 
between Wohler’s process and the metabolic changes by which urea is produced 
in the living body? What evidence have we that because an enzyme and an 
inorganic agent under different conditions give rise to the same end product, the 
driving force is the same, although the lines along which it is exercised are very 
different? JI think it is not the least of the many. services which Professor 
Meldola has rendered to chemistry, that he has given us this warning: ‘If we 
have gone so far beyond Nature as to make it appear unimportant whether an 
57 H. Pringsheim and H. Langshans, Ber. 1912, 45, 2533. 
58 For summaries of Willstatter’s and Marchlewski’s researches on chlorophyll, 
and of Piloty’s on hematin, cf. Annual Reports on the Progress of Chemistry 
(Gurney and Jackson) 1911, 8, 144-52; 1912, 9, 165-72. 
59 «Quite similar changes can be produced outside the body (in vitro) by the 
employment of methods of a purely physical and chemical nature. It is true 
that we are not yet familiar with all the intermediate stages of transformation 
of the materials which are taken in by the living body into the materials which 
are given out from it. But since the initial processes and the final results are 
the same as they would be on the assumption that the changes are brought about 
in conformity with the known laws of chemistry and physics, we may fairly 
conclude that all changes in living substance are brought about by ordinary 
chemical and physical forces.”—-Sir Edward Schafer, President's Address at the 
Dundee Meeting, British Association Report, 1912, p. 9. 
