Abstract
The inhibition of the succinic oxidase system (I) by p-chloromercuri-benzoate (V) was rapid, that of p-aminophenyl-arsenoxide (II), o-iodosobenzoate (III), and oxidized glutathione (IV) slow. The heart-muscle systems contained substances protecting I from II and III. II acted by inhibiting the succinic dehydrogenase. The inhibition was not reversed by dilution or washing away excess inhibitor. The action of II, III, IVwas reversed by BAL, V by cyanide. V reacted with one SH group, while II, III, IV required two. It was suggested that one SH group was necessary for the activity of succinic dehydrogenase.