CAP. II. DE MUSCULI

If the thick muscles of healthy animals are pounded with small rods, squeezed, and the slender parts scraped away, slender fibers remain in them, just as they do in those that are emaciated or starved to death.

But, if I am not mistaken, this does not prove that flesh is something different from muscular fibers, because whether the fibers are emaciated or not, if they are washed repeatedly with water, they always appear white under the microscope and have a similar tendinous consistency; no fuzz appears on them. In fact, in those very fleshy muscles that are thought to be encrusted with that fleshy fuzz, the fibers themselves appear to be of the same consistency and formed with the same columnar figure, in the same way as in muscles diluted with water, as can be seen in boiled or salted muscles.

It is true, however, that the slenderness and subtlety of the fibers in emaciated or compressed parts can depend on a lack of nutritive juice, which filled the pores of the fibers, just as occurs in dried-out sponges and withered tree leaves. In these, the fuzz does not fail, but only the juice which previously filled the spongy cavities. Hence it is gathered that the fibers of the muscles and the flesh are the same thing.

It must be noted, however, that muscular fibers differ from the fibers of tendons and membranes in that the former are spongy and are always moistened by blood, and by nervous and lymphatic juice, unlike the latter. They also differ in structure, in their very different way of operating, and in their energy, as we shall explain in its proper place.

PROPOSITIO III.

The species of muscles are enumerated.

In the last place, the various species of muscles must be enumerated, as well as what parts they act upon, and how, and through which directions. And first, I note that there are two species of muscles: some are composed of bundles of fleshy threads, which constitute a rectangular prism, as in Fig. 1, TAB. I, and these can be called straight prismatic.

Others constitute an oblique-angled prism, as in Fig. 2, TAB. I, and these can be called rhomboid.

Others have decussated crossed in an X-shape fibers composed of two rhomboids, as in Fig. 3, TAB. I, and can be called decussated.

Others consist of two non-decussated rhomboid bundles, as in Fig. 4, TAB. I, and are called penniform feather-shaped.

Others consist of fibers spread in an orbicular manner, and are called radiate.

Others are round, similar to rings, and are called circular sphincters.

Others consist of fibers wrapped around like a ball of thread, and are called spiral, orbicular.

I have also seen in the tail of a Gammarus crayfish/shrimp muscles woven not like a cloth, but composed of bundles of intertwined fibers, just as the hair of women is accustomed to be arranged.