Elements of Myology (Elementorum Myologiae Specimen)

A twofold description of a muscle may be provided, according to whether it is considered as formed from orders or from versus.

Muscle as it is composed of orders.

31. A simple rectilinear MUSCLE is a body composed of several orders that are equal, similar, and parallel to one another, and are so immediately imposed upon one another that the whole orders correspond to the whole orders.

Muscle as it is composed of versus.

32. Or a MUSCLE is a body composed of unequally equal versus, similar and arranged according to the excess of the tendons, where flesh is immediately imposed upon flesh, and tendons upon tendons, in such a way that the whole versus correspond to the whole versus.

33. From the definitions, it is evident that in whatever way a muscle is composed, there is in it one parallelepiped of flesh and two tetragonal prisms of tendons, in the manner I represented the muscle above. But since the thickness of the tendons has no use in explaining the movement of the muscle, and the part of them extending outside the flesh (which I call the projecting part of the continuous tendons) rarely produces a notable difference, it is better to consider only those planes of the tendons in which the extreme planes of the flesh are located, so that in a muscle, while we consider its movement, only three pairs of planes occur, to be designated by the same names that I used in the description of the flesh. These planes are the extreme planes, the transverse planes, and the lateral planes.

Extreme planes of the muscle.

34. THE EXTREME PLANES, composed of the extreme planes of the flesh immediately imposed upon one another, are rectangles under the transverse side and the tendinous side of the orders: