DESCRIPTIONE ET USU.

—then indeed, from the contraction of the fibers AB, GH, CD, the tendon BD with the attached weight R could be pulled obliquely upwards. But this hypothesis has no place in animals, in which such simple muscles having a rhomboid form are not found, whose tendon or mobile side BD would run within a smooth channel. Wherefore it must be concluded that such simple muscles are neither found in nature, nor do they act in the way those Illustrious Authors think. But such an action can take place only in some muscles composed of several rhomboids, as we shall explain in its proper place; but certainly not in those simple muscles which constitute a single rhomboid, of which the aforementioned authors speak in express words and exemplify with figures.

PROPOSITIO VI.

The true figure of the muscles is indicated.

That there exist in animals columnar muscles composed of fibers parallel to each other, such as ABDC, which pull a resistance R through the same direction of the fibers AB, is evident by autopsy direct observation/dissection, especially in the tongue of the woodpecker, and in the tails of crayfish, and in many others.

Furthermore, there are also simple rhomboid muscles AB, DC, Fig. 10, TAB. I, whose oblique fibers AB and CD, attached to bone TV, pull towards them another bone, or tendon RS, as are the muscles of the abdomen, the intercostals, and others, in which the resisting bone RS is moved by a transverse and parallel motion, approaching towards the firm bone TV; where it is to be noted that the angle VCD is not made less obtuse, but on the contrary, the obtuse inclination is increased.

In the last place, Fig. 11, TAB. I, there are penniform muscles, first observed and delineated by Casserio Placentino Giulio Casserio of Piacenza, an Italian anatomist. These are indeed most artfully formed for purposes to be exposed below; the oblique fibers act by contracting themselves, and from such oblique traction the suspended weight R is lifted in the same way as a weight is suspended by two or more ropes pulled obliquely, the force and mode of operation of which we shall declare in its proper place.

PROPOSITIO VII.

Muscles exercise a double force, proper and instrumental.

It is clear from experience that muscles exercise a double force: one is proper, depending on the very natural structure of the fibers; the other is—