Elements of Myology (Elementorum Myologiae Specimen)

Response to the second difficulty regarding the lateral planes.

...thin, so that their position relative to the transverse planes cannot be determined with certainty. But since we see in many places in collections of flesh that the lateral planes are perpendicular to the transverse planes, a similar position of the planes can be assigned, not without reason, to the individual muscles constituting those same collections. In the extreme planes of many muscles, it is clearly demonstrated by example that they are straight relative to the lateral planes, so that it may easily be admitted that the lateral planes are straight relative to the other four planes.

Response to the third difficulty regarding oblique angles.

As for the oblique angles, it is established by evident experiments that the extreme planes form oblique angles with the transverse planes, both in the extremities of the flesh freed from tendons, and in the middle of the flesh dissected by a plane parallel to the extreme planes.

Nevertheless, I would not wish to deceive the Reader, as if I had examined all the muscles of all animals and thus firmly believed that the position of the planes among themselves is the same in the flesh of all of them as I have just described. Wherefore, I only affirm with certainty here that I have found it so in most; and this is sufficient to demonstrate that this simple and regular construction of flesh is not asserted by me gratuitously as the measure of the others.

A geometric diagram depicts a longitudinal section of a muscle segment, modeled as a fleshy parallelepiped. The diagram shows a long, thin horizontal figure. The central portion is defined by points C and D at the top and A and B at the bottom. The figure terminates at its ends in points H (left) and G (right), forming pointed triangular extremities. Internal dashed lines connect point H to a point labeled E and point G to a point labeled F, illustrating the oblique angles described in the text.

What kind of planes of flesh?

4. From the definition of the fleshy parallelepiped, it is demonstrated,