222 P. P. Slonimski and H. de Robichon-Szulmajster 



individual purine and pyrimidine bases is even more striking 

 (Table VIII). Here again we find the same situation as in the 

 mutation study : adenine is the most effective of all the bases 

 studied and thymine is slightly more effective than uracil. 

 Adenine and cofactor E act synergistically while cofactor T is 

 inhibitory. Substances assayed for stimulation and found 



100 



?o» 



.jO co-fT E 



9' 



CONTROL 



^CO-F T 



HRS 



Fig. 3. Effect of commercial erythrose (0-5 



mg./ml.) or threose (1 mg./ml.) on respiratory 



adaptation. 



Adaptation in aerated phosphate buffer con- 

 taining 15 mg. glucose/ml. 



inactive are the following: D-glucose, D-ribose, 2-deoxy-D-ri- 

 bose, D-arabinose, L-arabinose, D-xylose, L-fucose, L-rham- 

 nose, D-erythrose, L-erythrose, L-erythritol, L-threose formate, 

 glycerol, ethanol, gluconic acid lactone, i-tartaric acid, 

 furfural, furfuryl alcohol, meso-inositol, ergosterol, tween 80, 

 yeast extract (Difco), casein hydrolysate (enzymic), vitamin 

 Bi25 folic acid, haemin, haematoporphyrin, mixture of trace 

 elements. 



