Note f — BOOK IV.

It is a farther manifest Indication of singular Design in the cartilaginous Rings of the aspera Arteria, that all the Way where they are contiguous to the Oesophagus, they are membranous, to afford an easie Passage to the Food; but after that, in the Bronchi; they are, some compleatly annular, some triangular, &c. And another observable is, the lower Parts of the superior Cartilages, receive the upper Parts of the inferior, in the Bronchi; whereas in the aspera Arteria, the Cartilages run and remain parallel to one another; which is a noble Difference or Mechanism in this (in a Manner) one and the same Part, enabling the Lungs and Bronchi to contract themselves in Expiration, and to extend and dilate themselves in Inspiration.