reproduce Figures 2 and 5 of chapter ix, from Rashevsky's Advances 



and Applications of Mathematical Biology, and Figure 1 of chapter 



xi from his Mathematical Biophysics. 



Finally, the authors wish to express their gratitude to the Prin- 



cipia Press and to the Dentan Printing Company for their unfailing 



efforts involved in publishing the book. 



Alston S. Householder 

 Herbert D. Landahl 



Chicago, Illinois 



October, 19U 



IV 



