PRESENT PROBLEMS 287 



did not attempt to secure evidence of their existence from the conduct 

 of the compounds containing them, another which kept in much 

 closer touch with the facts discovered in the laboratory. It was only 

 the latter theory which contributed much to the growth of our know- 

 ledge. A theory which cannot secure for itself a sound experimental 

 basis is, of course, of only ephemeral value. 



These, then, are the steps which have led to our present standpoint 

 in organic chemistry: The discovery of isomerism, the discovery of 

 radicals, the older radical theory, the theory of types, the establish- 

 ment of true molecular weights, the discovery of the fact of valence, 

 the determination of structure. 



I think that all workers in organic chemistry will accept the follow- 

 ing as a conservative statement of our present knowledge: (1) That 

 in organic compounds, at least, each atom is attached directly to only 

 a limited, small number of other atoms; (2) that in the sense of the 

 order of the successive direct attachments the structure of a very 

 large number of compounds is known with a degree of probability 

 that amounts to practical certainty. 



This brings me to the task which has been set, an attempt to out- 

 line the problems which lie before us in the further development of 

 our science. 



In the first place, there is still much to be done to extend our know- 

 ledge of compounds found in nature. This field is much less cultivated , 

 relatively, than was the case sixty years ago. There has been good 

 reason for this because of the problems of absorbing interest which 

 have arisen in the preparation and study of new compounds and in 

 the extension of our knowledge of old ones. But there must still re- 

 main many compounds to discover among both animal and vegetable 

 products. On this side organic chemistry resembles the descriptive 

 sciences of botany, zoology, and mineralogy. And just as botanists 

 think it worth their while to secure as complete a description as possi- 

 ble of the plants to be found on the earth, so it lies in our province to 

 isolate and identify the carbon compounds of the animal and vege- 

 table worlds with the difference that in our case each compound, 

 new or old, may be the starting-point for the preparation of an almost 

 endless number of others. But here most of us recognize that unless 

 a compound has some further interest than that it is new it is not 

 worth the time taken in its preparation. I am afraid, however, as we 

 look over the pages of our journals, there is too much evidence that 

 not every one lives up to this view. Our ever-increasing army of 

 nascent doctors must needs have something to do, and it is so easy 

 to make new compounds, and so difficult to find something new of 

 larger scope and really worth the doing. 



There still remains much to do in the determination of the struc- 

 ture of compounds which have long been known. The study of a 



