CELL-DIVISION AND DEVELOPMENT. 1 47 



information we possess shows us a combination of mechanical 

 with what we may term vital forces in the phenomena of Biology : 

 we must guard against being carried away by the apparently 

 beautifully simple explanations of the upholders of the physical 

 school, and at the same time we must recognize the contentions 

 of the Vitalists. Bunge,^ an ardent supporter of the latter 

 school, writing in 1889, says: " Je eingehender, vielseitiger, 

 griindlicher wir die Lebenserscheinungen zu erforschen streben, 

 desto mehr kommen wir zur Einsicht, dass Vorgange, die wir 

 bereits geglaubt batten physikalisch und chemisch erklaren zu 

 konnen, weit verwickelterer Natur sind und vorlaufig jeder 

 mechanischen Erklarung spotten." This represents the ideas 

 of the extreme Vitalistic school, and between it and the extreme 

 mechanical views a median ground, represented by the quota- 

 tion which I have made from His, exists. In the light of 

 recent investigations in cell-mechanics we must prepare our- 

 selves for the extension of the application of mechanical princi- 

 ples, but for the present we will do well to follow the advice 

 given by Phoebus to the headstrong Phaethon : " In medio 

 tutissimus ibis!' 



1 G. Bunge : Lehrbuch der physiologischen und pathologischen Chemie. Leip- 

 zig, 1889. 



