470 Mr. E. C. Grey. The Decomposition of 



Table TIL — Comparison of the Action of an Artificially Selected Strain of 

 B. coli communis (Escherich) on Glucose alone ; Glucose + Calcium 

 Formate ; Calcium Formate alone. 



Conditions of the experiment. 



Duration 



G-lucose before . . . 



„ after 



„ consumed 

 Formic acid before 



„ ,, after 



„ „ con- 

 sumed 



C0 2 total gas 



C0 2 from acids on 



chalk 

 C0 2 from formate 

 C0 2 from sugar ... 



G-lucose alone. 

 Medium not 

 neutralised during 

 fermentation. 



99 hours 

 3-385 

 3 -2276 

 -1574 

 None 

 -0874 



42 c.c. 

 41 „ 



Glucose alone. 

 Medium kept 

 neutral by 

 chalk. 



99 hours 

 1 -6926 

 1 -0628 

 -6098 

 None 

 -0249 



96 c.c. 

 90 „ 



6 c.c. 



Glucose + calcium 

 formate + chalk. 



120 hours 

 1 -6926 

 None 



I -6926 

 "5244 

 -0276 

 -4968 



291 c.c. 

 161 „ 



119 „ 



II » 



Calcium formate 

 alone. 



120 hours 

 None 



-5244 

 -4988 

 0256 



12 c.c. 



12 c.c. 



The medium contained in all cases 1 grm. peptone (Witte) in 100 c.c. 



The actual carbon dioxide produced by the organism from calcium formate 

 is in reality twice that actually evolved, for in the decomposition 



(HCOO) 2 Ca + H 2 = CaC0 3 + C0 2 + 2H 2 



it is clear that one-half of the C0 2 is retained in combination with the 

 calcium. 



These results bring out, therefore, very clearly one object which is attained 

 by the decomposition of formates by these bacteria, viz. : that the organisms 

 are thereby supplied with the best possible neutralising agent. For the 

 formate by being decomposed into carbon dioxide and hydrogen virtually 

 liberates alkali within the bacterial cytoplasm, and thus not only neutralises 

 the medium, but also the bacteria themselves. Moreover the calcium formate 

 being itself neutral possesses none of the disadvantages which would arise 

 from the presence of even a slight excess of alkali. It would be difficult to 

 devise a more efficient means for maintaining neutrality in this case. I 

 would suggest the utilisation of sodium or calcium formate as a neutralising 

 agent in working with those organisms capable of decomposing it, especially 

 for solid media, with which the addition of dissolved alkali from time to time 

 would be impracticable. 



