INTRODUCTION 3 



mechanical explanation of morphological results, and according to this con- 

 ception physiology would constitute the very summit of all biological investi- 

 gation. It is scarcely necessary to remark that in the present state of our 

 knowledge we cannot yet forecast how this far-distant goal shall be reached. 



REFERENCES. Helmholtz, " Uber die Wechselwirkung der Naturkrafte und 

 die darauf beziiglichen neuesten Ermittlungen der Physik " (1854). "Uber die 

 Erhaltung der Kraft " (1862) in " Vortrage und Reden " by Hermann v. Helm- 

 holtz. I. Braunschweig, 1884. 



