176 LAURENCE F. FOSTER 



rate of growth of organisms as affected by different temperatures 

 and has demonstrated a conformity of her curves with the Van't 

 Hoff-Arrhenius law within certain limits. 



The various other phases in the hfe of a culture have been 

 investigated to a less extent but from the work of Buchanan 

 (1918) and Ledingham and Penfold (1914) it seems probable 

 that growth is a discontinuous process in the sense that develop- 

 ment of a given organism is dependent upon different laws in the 

 successive phases of the Ufe of the culture. 



An illustrative curve follows: 



Fig. 2. Illustrative Curve of Acid Formation by Streptococcus 



HEMOLYTICUS IN GlUCOSE BrOTH 



(1) Initial stationary period. 



(2) Lag period. Acid formed at a slowly increasing rate. 



(3) Maximum period. Acid formed at a constant, maximum rate; curve 

 is an oblique, straight line. 



(4) Period of negative acceleration. Acid formed at a decreasing rate. 



(5) Maximum stationary period. Final Ph has been attained; curve is a 

 straight line parallel to the abscissa. 



