A separate contractile mechanism for tonus in unstriated muscle

Summary

• (1) At 20° C., dog’s stomach muscle shows the first asphyxiai contraction, but not the second.

• (2) At 20° C., glucose loses its inhibitory action, but that of oxygen is increased; at higher temperature, the reverse happens.

• (3) At 20° C., iodoacetic acid and cyanide also do not produce contraction.

• (4) If the second asphyxiai contraction is prevented mechanically or if developed, is abolished mechanically, then the power to contract on asphyxiation is permanently lost. Twitch contractions can be produced, but not tonic contractions. This suggests a separate contractile mechanism for tonic contraction (alactic tone).