The _Rectus_ or _Longus_ begins in the side of the four upper _Vertebra's_ of the Back, and is join'd to the upper _Vertebra's_ of the Neck, and the hinder part of the Head. The _Spinatus_ hath its Origine in the fourth and fifth upper _Vertebra's_ of the Back, and is fasten'd to all the six lower _Vertebra's_ of the Neck. The _Transversalis_ springs forth out of the upper _Vertebra's_ of the Back, and cleaves to the Extremity of the four _Vertebra's_ of the Neck. * * * * * {31} CHAP. VIII. _Of the Myology or Anatomy of the Muscles of the Chest; or of the Breast Belly, and Back._ _How many Muscles are there in the Breast, and which be they?_ The Breast hath fifty seven Muscles, that is to say, thirty that serve to dilate it, twenty six whose Office is to contract it, and the _Diaphragm_ or Midriff, which partakes of both Actions. The thirty which dilate the Breast are equally plac'd to the number of Fifteen, _viz._ the _Subclavius_, the _Serratus Major Anticus_, the two _Serrati Postici_, and the eleven external _Intercostals_. The twenty six which contract the Breast are likewise equally rank'd to the Number of thirteen on each side, _viz._ the _Triangularis_, the _Sacrolumbus_, and eleven internal _Intercostals_. The _Subclavian_ takes up the whole space between the Clavicle and the first Rib: Its Original being in the internal and lower part of the _Clavicula_, and its insertion in the upper part of the first Rib. The _Serratus Major_ is a large Muscle having seven or eight Indentings or Jaggs. It takes its rise in the interior Basis of the _Omoplata_ or Shoulder-Blade, and its Jaggings are inserted in {32} the five lower true Ribs, as also in the two upper spurious Ribs. The _Serratus Posticus Superior_, begins with a large _Aponeurosis_ in the _Apophyses_ of the three lower _Vertebræ_ of the Neck, and of the first of those of the Back; then passing under the _Rhomboid_, it is join'd obliquely by four Indentings to the four upper Ribs. The _Serratus Posticus Inferior_, commences in like manner with a large _Aponeurosis_ in the _Apophyses_ of the three lower _Vertebra's_ of the Back, and of the first of those of the Loins, and is afterwards fasten'd by four Digitations to the four lower Ribs. The eleven _External Intercostal_ Muscles are situated in the spaces between the twelve Ribs passing obliquely and on the outside from the back part to the fore part. They take their rise below the Upper Rib, and have their Insertion above the lower Rib. The _Triangularis_ is the first of those that contract the Breast, and possesseth the inward part of the _Sternum_: Its Original is in its lower part, and its Insertion in the top of the Cartilages of the two upper Ribs.