The text describes various muscles and their anatomy, focusing on the Latissimus as the widest muscle with complex functions, originating from the sacrum and lumbar regions. It discusses the Sacro-Lumbus muscle, emphasizing its role in binding ribs and constricting the torso to assist in expelling air. Additionally, the Pectoralis muscle is detailed, noting its structure and connection to other muscles, supporting arm movement and illustrating its importance in human figure studies.
Muscles in Service of the Muscles.
...the neck of the upper arm bone around (23) works in contrast to the Triangular Shoulder Muscle (14) See the Rotundus Major in Illustrations B. and C.
17. Latissimus or the Broad Back. This muscle is the widest of all, with various fibers that pull the arm backward in diverse ways, although always slightly crooked; it has three unequal angles: two long and one short. It originates with a broad nervous start from the spine of the sacrum and lumbar regions (12), also from the upper part of the Ilium or hipbone (34) &c. From there it climbs upwards entirely muscular, and adheres slightly to the rear corners of the shoulder blade, around (19) and inserts itself with a connected cord under the head of the upper arm bone (23). See this Latissimus in Illustrations B. and C.
18. Sacro-Lumbus or Holy Lower Back Muscle. Partly lies under the aforementioned Latissimus (17), emerging with a nervous skin from the sacrum (12) clinging to the vertebrae of the lower back and sends as many tendons from it that it can bind to all the ribs. Its function is to haul the ribs together, tighten the torso, and expel wind. See Illustration C.
19. Pectoralis or Chest Muscle, this is a large and fleshy muscle; it pulls the arm forward in various ways: has a pentagonal shape, therefore called the Old Pentagonus. It springs from over half of the collarbones (14) and almost the entire chest bone (13) of the 5th, 6th, and 7th rib, with a broad fleshy start and implants itself with a double tendon, between the muscle Deltoides (14) and the following muscle Biceps (20)...