Tendons Without Muscle and the Body's Sesamoid Bones
The great wrist tendon, the eight sesamoid bones, and the three-part muscle from breastbone to pubis.
This page of the Treatise on Painting continues the survey of the muscles (throat, shoulders, stomach) and then turns to three anatomical chapters. One describes the largest tendon in man, at the wrist, which has no muscle and binds the two bones of the forearm together. Another counts eight small bones fixed within the tendons at the shoulders, knees and feet, which harden with old age; a third describes the muscle running from the breastbone to the pubis, divided lengthwise by three tendons into three powers.
On this page
The great wrist tendon that binds the forearm bones
Chapter [342] describes the largest tendon in man, found where the arm meets the palm near the four fingers. Square in shape, about three fingers wide and half a finger thick, it runs between the two bones of the forearm and serves only to hold them tightly together so they do not spread apart.
The eight sesamoid bones set within the tendons
Chapter [343] counts eight small bones fixed in the middle of the tendons at certain joints: one in each shoulder, one in each knee, and two in each foot beneath the first joint of the big toe toward the heel. These grow very hard toward old age.
The three-part muscle from breastbone to pubis
Chapter [344] describes a muscle rising near the breastbone (the 'pomegranate') and ending at the pubis, of three powers because divided along its length by three tendons: first the upper muscle, then a tendon as wide as it, then (continued on the next page).