A Histochemical Study on the Intrinsic Laryngeal Muscles

Abstract

Histochemical demonstrations of lipoid, succinic dehydrogenase and phosphorylase were done in the intrinsic laryngeal, the heart, the diaphragm and the femoral muscles of the dog.
The results obtained were as follows:
1). The intrinsic laryngeal muscles were chiefly composed of two kinds of muscle fibers, i. e. the one which shows a high enzymatic activity of succinic dehydrogenase and an intense affinity to Sudan Black B and the other which gives very low activities of them. The former corresponds to the red muscle fiber and the latter to the white fiber. Besides these muscle fibers, there exist a few muscle fibers of intermediate type which show a moderate enzymatic activity.
2) The distribution ratio of the red muscle fibers to the white was approximately 1: 1 in every intrinsic laryngeal muscle, while it was 1: 1.5 in the femoral muscle.
3) In general, the peripheral parts of the muscles were predominant in white fibers, while the central parts in red ones. In the thyroarytenoid muscle, the distribution ratio of the red muscle fibers to the white was approximately 1: O.9 in the central parts and 1: 2.3 in the peripheral parts.
4) The activity of phosphorylase was high in the femoral muscle, medium in the intrinsic laryngeal muscles and low in the diaphragm and the heart muscle.
5) The function of the intrinsic laryngeal muscles is considered more tonic than that of the femoral muscle and more phasic than that of the heart and the diaphragm muscle.