Date of Award

3-1941

Document Type

Thesis - Restricted

Degree Name

Master of Science (MS)

Department

Medical

First Advisor

Eben J. Carey

Abstract

In all the investigation of red and white muscle in the last fifty years, one observation alone ·remains unchallenged. That is the law that the more continuous the activity, the redder the muscle. Its quick, hopping motion--a hop and a pause--is characteristic of the action of white muscle. Its heart which beats continuously is practically the only red muscle in the animal. The bird that uses its wings almost continuously has red pectoral muscles. The breast of the fluttering domestic hen is composed of "white meat". In the lower mammalian forms some muscles are almost entirely white and others, entirely red. Phylogenetically, the higher the animal , the
more mixed is its skeletal muscle, until, in the study of the muscles of man one finds that nearly all muscles are of the mixed variety. In the rabbit, certain muscles of the hind leg are clearly white: semimembranosus , adductor magnus; and others, red: semitendinosus, soleus. It is the rabbit, tnerefore, that has been used most as experimental animal in the anatomical and physiological study of red and white muscle.

At the present time it is generally believed that the red muscle is composed principally of narrow, coarsely striated fibers and that white muscle is made up principally of wide, finely striated individual fibers. While studying the effects of various drugs and physical agents on the motor nerve ending in striated muscle* it was observed that

*Results to be presented before the Anatomical Association Meeting this year in collaboration with Dr . Carey.

the muscle fibers of the animals killed with a drug or agent which severely increased their activity--insulin, metrazol, electricity--appeared to be preponderantly of the wide, finely striated variety, whereas the muscle fibers of animals killed with a depressant--magnesium sulfate, cold--were preponderantly of the narrow, coarsely striated type. So striking was the finding (in the case of the intercostal, abdominal,
and limb muscles of the rat) that the presence of wide, finely striated fibers is the morphological expression of heightened activity , and the narrow , coarsely striated, of lowered activity, that it was decided to reopen the question of the histology of red and white muscle , and since the original investigations were made using the rabbit, it was decided to use the rabbit also in this work.

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