RESPIRATORY METABOLISM 377 



respiratory enzyme system plays no part in the respiration of Paramecium. 

 Peters (1929) obtained no inhibition with M/500 KCN on Colpidium 

 colpoda. The data of Pitts (1932) for C. campylum shows that less than 

 20 percent of the respiration is cyanide sensitive and that this depression is 

 only temporary, and that while still in cyanide the respiration may rise 

 to a rate which is as much as 25 percent above normal and drop again 

 to 80 percent of the normal rate. M. Lwoif (1934) found that the 

 respiration of Glaucoma prriformh in peptone solution was depressed as 

 much as 80 percent during the first half hour, but that by the third 

 hour the rate had returned to normal (M/1,000 KCN), or almost 

 normal (15 percent below in M/450 KCN), and then decreased. In a 

 weaker KCN solution (M/4,500) this latter decrease did not occur. 

 The organisms were able to live twenty- four hours in M/450 KCN 

 and eight days in M/1,000, but they did not divide. In M/2,000 and 

 M/5,000 KCN multiplication of the organisms occurred slowly. In 

 glucose-Ringer solution, M/450 KCN did not inhibit, but produced an 

 acceleration of as much as 36 percent during the first half hour. The 

 conclusion to be drawn from these data is that the ciliates, as far as we 

 know, are relatively insensitive to the action of cyanide, and we might 

 consider the temporary inhibitions produced in some cases as secondary 

 effects rather than direct effects upon the respiratory mechanism (cf. 

 another explanation mentioned below). It would be interesting to rein- 

 vestigate the effect of KCN on some of these ciliates by the use of 

 balanced KCN-KOH solutions. It seems possible that the data, especially 

 in the case of the temporary effects, may be complicated by the loss of 

 KCN from the experimental solution to the KOH solution. 



Among some of the flagellates, however, there seems to be quite a 

 different respiratory mechanism. A. Lwoff (1933) found that M/3,000 

 KCN inhibited respiration of Strigomonas oncopelti 90 percent, of 

 5". jasciculata 83 percent, and of Leptofnonas ctenocephali 95 percent. 

 With M/1,000 KCN, both species of Strigomonas were inhibited 90 

 percent, and L, ctenocephali 95 percent. The latter species was extremely 

 sensitive and was inhibited 92 percent by M/20,000. Growth was also 

 decreased in those concentrations which inhibited respiration, and the 

 organisms were killed only by much greater concentrations. M. Lwoff 

 (1934) reported an inhibition of 90 percent for Polytoma uvella, and 

 Jay (1938) an inhibition of 60-65 percent for Khawkinea and Astasia 



