Histochemical and morphometric studies on the foreleg musculature of sheepwith respect to its function .1. Flexors and extensors of the elbow joint

Muscle tissue was removed from the extensors and flexors of the elbow joint of six male sheep (180 days old) and stained for NADH tetrazolium oxidored uctase and myofibrillar ATPase after preincubation at pH 4.3 in order to id entify three fiber types: slow twitch oxidative (STO), fast twitch oxidativ e (PTO) and fast twitch glycolytic fibers (FTG). The medial head of the M, triceps brachii and the anconaeus muscle had the largest fibers (> 50 and 60 mu m). The smallest muscle fibers (35-43 mu m) were found in the dorsal part of the long head of the triceps muscle. The m edial head of the triceps muscle and the anconaeus muscle possessed a very high percentage of STO-fibers (90 and 100%) and FTG-fibers were absent in t hese muscles. In the other extensors and flexors of the elbow joint the STO -percentage amounted to less than 30%. The dorsal part of the long head of the triceps muscle contained only 13% STO-fibers, but had the highest perce ntage of FTG-fibers (49%), which is representative of fast-muscles. The muscles of the elbow joint perform both static and dynamic functions. T he medial head of the triceps brachii muscle and the anconaeus muscle posse ss the complement of enzymes which permits them to fulfil the work of exten sors in the standing position. Therefore, they are typical of antigravity m uscles. The histochemical structure of the other extensors and flexors refl ect their function in motion. The lateral and long head of triceps muscle o ppose the flexors and extend the elbow joint of the raised limb in the swin g phase, during the landing phase they also function to support the other e xtensors of the elbow.