Note m — BOOK IX.
Reading edition
The Tail is the grand Instrument of the Motion of the Body; not the Fins, as some imagine. For which Reason, Fishes are more musculous and strong in that Part, than in all the rest of their Body, according as it is in the motive Parts of all Animals, in the pectoral Muscles of Birds, the Thighs of Man, &c.
If the Reader hath a Mind to see the admirable Method, how Fishes row themselves by their Tail, and other Curiosities relating to their Swimming; I shall refer him to Borelli de mot. Anim. Part. 1. Chap. 23. particularly to Prop. 213.