EMBRYOLOGY AND MEDICAL FRO GEE SS 19 



of protoplasm goes on the power of growth diminishes. I consider it 

 probable that the growth and differentiation of protoplasm is the direct 

 cause of the diminution of the growth power. The observations on 

 growth bring out clearly to our minds the conception that the decline is 

 by far the most rapid in the very early periods of embryonic develop- 

 ment or, better expressed, that the rate of decline is at its maximum 

 during the earliest periods. The older the individual becomes the less 

 is the power of growth, but also the less rapid is the decline in that 

 power. Thus we reach the paradoxical conception that the period of 

 most rapid development is also the period of most rapid decline. This 

 view, it seems to me, applies to all development, at least in the higher 

 animals. As I have spoken on this subject more fully elsewhere, I 

 will not pursue it longer now, but it seemed to me desirable to refer 

 to it as an illustration of the far-reaching character and wide scope of 

 embrvoloo'ical investigation, which inevitably allies itself with every 

 other biological science. 



It would be no difficult task to extend my discourse by multiplying 

 illustrations of the beneficial influence of embryology upon other de- 

 partments of medical science. It is one of the institutes of medicine — 

 a part of the foundation of knowledge upon which medical practise 

 is erected. 



Embryology supplies facts which are directly valuable to the prac- 

 titioner. It supplies explanations and interpretations of many ana- 

 tomical structures and relations which would otherwise remain incom- 

 prehensible. It supplies the clues to many common and rare anoma- 

 lies, and it supplies to pathology a series of fundamental conceptions, 

 without which our actual present pathological knowledge could not 

 have been upbuilt. These claims of embryology to recognition are 

 very great, but nevertheless they do not include her greatest claim to 

 a preeminent place among the medical sciences. That greatest claim 

 is established in my opinion by the contributions of embryology to the 

 solution of the problem of organic structure. 



Structure is the only distinctive mark of living bodies, by which 

 we know them to differ from inanimate objects. In the final dis- 

 crimination between living and dead all other distinctions fail us or 

 at best are utterly uncertain. In the higher forms we see differences 

 of function always correlated with visible differences of structure. 

 From such evidence, together with much other, we have established 

 the hypothesis or theory — for at best it is only a theory — that all living 

 functions are dependent upon organic structure. It is quaint, we may 

 remark in passing, to read in recent essays by a learned German 

 botanist the announcement of this theory, which the vast majority of 

 biologists have long adopted, as a new foundation for biological phi- 

 losophy, because he terms the ultimate unknown facts of structure 

 ' Determinanten.' How often has science been impeded by the intru- 



