OUR LIFE. 49 



1866 1 is completely established by an accurate study 

 of the unicellular protozoa, and that " the psychic 

 phenomena of the protistae form the bridge which 

 unites the chemical processes of inorganic nature with 

 the mental life of the highest animals." Verworn 

 has further developed these views, and based them 

 on the modern theory of evolution, in his General 

 Physiology. This distinguished work returns to the 

 comprehensive point of view of Johannes Miiller, in 

 opposition to the one-sided and narrow methods of 

 those modern physiologists who think to discover the 

 nature of the vital phenomena by the exclusive aid of 

 chemical and plrysical experiments. Verworn showed 

 that it is only by Miiller' s comparative method and by 

 a profound study of the physiology of the cell that we 

 can reach the higher standpoint which will give us a 

 comprehensive survey of the wonderful realm of the 

 phenomena of life. Only thus do we become convinced 

 that the vital processes in man are subject to the 

 same physical and chemical laws as those of all other 

 animals. 



The fundamental importance of the cellular theory 

 for all branches of biology was made clear in the 

 second half of the nineteenth century, not only by 

 the rapid progress of morphology and physiology, but 

 also by the entire reform of that biological science 

 which has always been deemed most important on 

 account of its relation to practical medicine — patho- 

 logy, or the science of disease. Many even of the 

 older physicians were convinced that human diseases 

 were natural phenomena like all other manifestations 

 of life, and should be studied scientifically like other 



1 Zell-seelenund Seelen-zellen. Ernst Haeckel. Gesammelte populdre 

 Vortrcige. I. Heft. 1878. 



