RESPIRATORY METABOLISM 379 



sensitive fraction (90 percent) of S. fasciculata respiration was also 

 sensitive to CO. In an 80/20 mixture of CO/O, inhibition was 61 percent, 

 in 95/5 mixtures 85 percent, and in 98/2 mixtures 90 percent. Values 

 of K for the Warburg-Negelein equation 



A CO 



where A is O, consumption in the CO/Oo mixture and A,, is O. con- 

 sumption in the control, varied from 2.58 in 80 percent CO to 5.3 in 

 98 percent CO. M. Lwoff found that carbon monoxide (2-5 percent Oo 

 in CO ) produced the same effect on Glaucoma as KCN in both peptone 

 and in glucose-Ringer solutions. In peptone there was a marked inhibi- 

 tion for the first half hour and then a return to normal or almost normal, 

 and in glucose-Ringer there was an increase of 20 percent. Reidmuller 

 (1936) reported no appreciable effect of CO on O. consumption for 

 Trichomonas joetus in 95/5 mixtures of CO and Oo. The effect of KCN 

 was not investigated. The effect of CO on other Protozoa should be in- 

 vestigated together with the effect of cyanide. Recently azide (HN3) 

 has been found to have an effect on respiration which is similar to but 

 not identical with that of HCN and CO (Keilin and Hartree, 1936; and 

 others), and it would be interesting to make comparisons of these re- 

 agents on protozoan material. 



For the purpose of inhibiting the cytochrome-cytochrome oxidase sys- 

 tem, CO is apparently much more specific then HCN or azide. This is 

 especially true if inhibition accurs in the dark but not in the presence 

 of bright light, because the inactive compound formed by CO and 

 cytochrome oxidase is dissociated upon illumination into CO and active 

 oxidase. The reversibility upon illumination of CO inhibition has not 

 been investigated for Protozoa. 



The distribution of cytochrome among the Protozoa is a relatively 

 untouched subject. A. Lwoff (1933) found two absorption bands in 

 Strigomonas fasciculata, one at 530, and another rather broad band at 

 555 mp. These bands disappeared upon passage of O2 through the solu- 

 tion. Upon addition of KCN no other bands became visible, and the 

 question arises as to whether the 555 band was the b and c bands of cyto- 

 chrome or the b band of the hemochromogen, as has been found for 

 various bacteria. Lwoff found the 555 band also in S. oncopelti, Glau- 



