There are three, viz. the Sphincter, and two Levatores. The Sphincter is two Fingers broad, to open and close the Rectum. This Muscle being double, is fasten'd in the fore-part to the Penis in Men, and to the Neck of the Matrix in Women, as also behind to the Coccyx, and laterally to the Ligaments of the Os Sacrum, and the Hips.
The two Levatores arise from the inner and lateral part of the Os Ischion, and are fasten'd to the Sphincter of the Anus, to lift it up after the expulsion of the Excrements.
The Bladder hath also a Sphincter Muscle to open and shut its Orifice.
C H A P. X.
Of the Muscles of the Omoplatæ, or Shoulder-Blades, Arms, and Hands.
How many ways doth the Omoplata or Shoulder-Blade move, and what are its Muscles?
The Omoplata moves upward, downward, forward, and backward, by the means of four proper Muscles, which are the Trapezius, the
Rhomboides, the proper Levator, and the lesser Pectoral, or Serratus Minor Anticus.
The Trapezius or Cucullaris hath its beginning in the back part of the Occiput, or hinder part of the Head, in the Spines of the six lower Vertebra's of the Neck, and of the nine upper of the Back, in passing from whence it is implanted in the Spine of the Omoplata or Shoulder-Blade, and the external part of the Clavicula, as far as the Acromion. This Muscle produceth many Motions by reason of its different Fibres, drawing the Shoulder-Blade obliquely upward, downward, and forward.