#acrum

• Sacrum — An obsolete, rare graphic variant or faulty transcription for the sacrum bone (os sacrum); the large triangular bony piece located at the base of the vertebral column, formed by the structural fusion of the five sacral vertebrae, articulating laterally with the iliac bones to close the pelvic girdle.
• To sour — To subject a material, food, or substance to a controlled souring or acid fermentation process; to become sour. In certain old crafts or technical contexts (such as tanning or textile preparation), the action refers to the structural chemical treatment of fibers or hides in weak acid solution baths to modify their physical properties of elasticity and resistance.
• Ambulacrum — An anatomical formation specific to echinoderms, represented by a groove, a perforated zone, or a radial band along the body, through whose openings the hydraulic (ambulacral) feet protrude. Also, the term can broadly designate the entire water vascular system, being the core structural element that differentiates this class of marine invertebrates within the animal kingdom.