404 PHYSIOLOGY 



ready almost entirely isolated. Indeed the isolating differen- 

 tiation began its destructive work, even in its own special realm. 

 This was the time when, in Germany, Hoppe-Seyler's efforts were 

 directed toward the separation of physiologic chemistry as a sepa- 

 rate science. If he had succeeded, the individual branches of 

 physiology itself would have lost sympathy with one another. This 

 danger now appears to be past, although now and then a voice is 

 still heard in favor of the separation of physiologic chemistry. 

 But even without this, the whole development of physiology is 

 a classic example of the constantly increasing tendency of the pre- 

 sent day toward differentiation of special branches. 



At a time when the expansion of separate branches has reached 

 as extreme a degree as at present, at a time when the immersion 

 in certain special questions threatens to result in a complete loss 

 of relationship, and, in fact, has already partly succeeded, at such 

 a time the need of compilation makes itself more and more felt. 

 This has already been recognized in this country, in which the 

 restricting fetters of tradition and historic development do not 

 weigh so heavily as in the Old World. Compilation was, therefore, 

 the word which has brought us together to-day. As concerns my 

 own branch, I must greet this tendency with especial joy. Per- 

 haps the spirit of union, which is felt here to-day, will succeed in 

 reviving the natural relations which unite physiology with so many 

 other sciences, to the mutual advantage of all branches and to 

 the furthering of human knowledge. 



If I attempt in the following to sketch briefly the manifold 

 relations of physiology, I will turn my attention above all to those 

 relationships from which we may expect in the future especial 

 advantages for the further development of our knowledge. 



The natural relationships between physiology and other sciences 

 follow of necessity from the aim which the former follows. Physi- 

 ology is the science of life. In this conception there is universal 

 agreement. We may clothe this naked definition in different gar- 

 ments, but its germ remains always the same. The general aim of 

 all physiologic investigation is the analysis of the phenomena of 

 life. We may ask, however, what principle should physiologic 

 investigation follow in this analysis; but in regard to this there 

 has not always been universal agreement. Different periods and 

 different investigators have given different opinions. We have 

 varied often between purely mechanical and more mystical prin- 

 ciples. First one, then the other, has ruled alone. At times the 

 adherents of the first, at times those of the second have increased. 

 After a long period, full of valuable results, in which the purely 

 mechanic consideration of life-phenomena ruled, the pendulum has 

 swung again, in the last decennium of the past century, toward 



