Myographia nova sive Muscolorum omnium (in copore humano hactenus repertorum) accuratissima descripto, in...

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Tab. 4.

The Pyramidal or Supplementary muscle.

This draws the abdomen inward.

It takes its name from the shape of a pyramid, which it accurately imitates. It arises broad and fleshy from the exterior part of the pubic bone, and passing somewhat beneath the rectus straight muscle, it is inserted by a long and round tendon into the linea alba white line. These muscles are sometimes found to be absent in those who do not have the origin of the ascending muscle from the iliac bone, but rather from a strong ligament passing internally from the spine to the pubic bone, and who are endowed with four perigraphae tendinous intersections in the rectus.

Andreas Vesalius, Adreanus, and Columbus all agree that the pyramidal and the rectus muscles share the same origin, but they are mistaken; for we can affirm with certainty that these muscles are most clearly distinguished from one another.

Fallopius, their first investigator, places their action in compression and affirms that they promote the excretion of urine. Laurentius says that if one of this pair operates separately from its companion, the linea alba is pulled downward obliquely; if both concur in acting simultaneously, it is drawn directly and perpendicularly, and at the same time, the groin and the bladder are compressed when urine is passed at will. Columbus holds that the erection of the penis is greatly aided by these muscles, but his opinion is not approved by Lloyd because of the location; besides the fact that they do not reach the penis anywhere, they are also clearly found in females.