It is a Cavity in which the Heart and the Lungs are principally enclos'd.
What is to be consider'd outwardly in the Breast?
Its extent, and the situation of the Parts therein contain'd.
What is its extent?
It is extended from the Clavicles to the Xiphoides, or Sword-like Cartilage on the fore-part, and bounded on the hinder by the twelfth Vertebra of the Back, having all the Ribs to form its Circumference, and the Diaphragm for its Bounds at bottom, separating it from the Abdomen or lower Belly.
What is the situation of the Parts contain'd in the Breast?
The Lungs take up the upper Region, and fill almost the whole Space, descending at the distance of two Fingers breadth from the Diaphragm; the Heart is situated in the middle, bearing its Point somewhat towards the Left side, under the Lobes of the Lungs, which are divided by the Mediastinum that distinguishes them into the Right and Left Parts.
How is the Breast Anatomiz'd or open'd?
After the dissection of the five Teguments, and the removal of the Muscles, as in the lower Belly, the Anatomist proceeds to lift up the Sternum or Breast-Bone, by separating it from the Ribs; then it is laid upon the Face, or else entirely taken away, to the end that the internal Parts of the Breast may be more clearly discover'd; whereupon immediately appear, the Heart, the Lungs, the Diaphragm, and the Mediastinum, which sticks to the Sternum throughout its whole length.