COMPARATIVE STUDIES ON RESPIRATION. 



XIV. Antagonistic Action of Lanthanum as Related to" 



Respiration. 



By matilda MOLDENHAUER BROOKS. 

 {From the Laboratory of Plant Physiology, Harvard University, Cambridge.) 



(Received for publication, July 8, 1920.) 



In previous papers^ -^ the writer has discussed the relation between 

 respiration and antagonism, including antagonism between mono- 

 valent cations and bivalent cations. The present paper extends 

 these studies to trivalent cations. 



The experiments were made upon Bacillus suhtilis. The method 

 of experimentation has been fully described in previous papers. 



The results are shown in the figures. Fig. 1 shows the manner in 

 which the rate of respiration changes under the influence of La(N03)3 

 in concentrations of 0.000006, 0.000025, 0.00005, 0.05, and 1.0 m. 

 During the first 10 minutes the bacteria are under normal conditions 

 and the curve (broken line) is horizontal. After this (at the point 

 marked on the abscissa) the salt is added. The addition of suffi- 

 cient La(N03)3 to make the concentration 0.000006 m produces an 

 increase in the rate which remains constant during the period of 

 experimentation. When the concentration is 0.000025 m the rate 

 is normal, while in higher concentrations there is a decrease in rate 

 which amounts almost to a cessation of respiration at 1 m. These 

 curves are selected from a number of similar typical curves and each 

 represents one experiment. 



Fig. 2 shows the effect of various concentrations of La(N03)3 upon 

 the rate of respiration. The rate indicated is that produced after the 

 bacteria had been in contact with the salt for 1 hour. There is an 

 increase in the rate of production of CO2 at 0.000006 m and a decrease 

 in the rate at concentrations higher than 0.000025 m. As the effect 



1 Brooks, M. M., J. Gen. Physiol, 1919-20, ii, 5. 



2 Brooks, M. M., J. Gen. Physiol, 1919-20, ii, 331. 



337 



