2o POPULAR SCIENCE MONTHLY 



sion of a pedantry which mistakes the invention of a new term for 

 the introduction of a new idea ! 



To find out what structure really is is the goal of all biological 

 science. When we discover this secret, we may hope to discover also 

 how structure functions and why it exists. The problem of structure — 

 of organization — is double; there is first the question, what are the 

 essential qualities of the structure of living matter as such, and there 

 is, second, the question of the variations and specializations, which 

 structure may undergo. With both of these questions embryology is 

 confronted and both of them it is seeking to answer. The first is 

 the riddle of life. Embryologists are bravely attacking it and have, I 

 believe, already made a little real progress towards its solution. To 

 them it presents itself as a series of queries concerning the germ-cells 

 and the fertilized ovum. Searching analyses of the details with the 

 highest powers of the microscope and the most refined technique 

 coupled with experiments have indeed increased our knowledge of the 

 organization of the germ cells. America, thanks to the brilliant work 

 of E. B. Wilson and E. G. Conklin, and of their associates and fol- 

 lowers, occupies a leading position in this difficult exploration. The 

 importance of knowledge of the fundament of organic structure can 

 hardly be exaggerated, and when it is obtained it will, I may prophecy, 

 have profound far-reaching and enduring effects upon all medical 

 science. 



Even more intimately is embryology occupied with the second part 

 of the problem of structure, namely, the question of differentiation, 

 i. e., of the gradual production of the varied organization of the adult 

 with almost innumerable unlike parts. To-day the central problem of 

 biology is that of differentiation, and the main purpose of cotemporary 

 embryological research is to attack that problem. The problem is 

 three-fold, for we must learn what differentiation is, how it is pro- 

 duced, and why it is produced. Embryology might almost be termed 

 the science of organic differentiation. Xow all that you do, as prac- 

 tising physicians, is to deal with differentiated organs and tissues. You 

 deal with a function, normal or diseased, which is rendered possible by 

 the differentiation of cells. You deal with pathological states, every 

 one of which has its special differentiation. Every phenomenon which 

 you encounter in your professional work is conditioned by the differ- 

 entiation of the organic living substance. To regulate that differ- 

 entiation, to set it right when it has gone wrong, is the brightest 

 vision of future human power which I can conceive, and I can not but 

 think of embryology, which strives unceasingly to discover the laws of 

 differentiation, as that Institute of Medicine which is to be the founda- 

 tion of a greater practical medical progress than any yet achieved. 

 The physician's knowledge is the mother of mercy. 



