Building on the theory of mechanics as formulated by Aristotle and Galileo, and countering objections expressed by Stephani degli Angeli among others, Borelli presented a completely mechanical account of the action of muscles and analyzed the way the center of gravity of an animal shifts in locomotion. Translated into English by Paul Maquet as Borelli's on the movement of animals - On the force of percussion. Berlin: Springer, 2015. Digital facsimile of the 1667 edition from Google Books at this link.

Borelli originated the neurogenic theory of the heart’s action and first suggested that the circulation resembled a simple hydraulic system. He was the first to insist that the heart beat was a simple muscular contraction. One of the founders of biomechanics, Borelli was a representative of the Iatro-Mathematical School, which treated all physiological happenings as rigid consequences of the laws of physics and mechanics.

Borelli’s experiments included what are probably the first measurements of masticatory force.

English translation by P. Maquet from the 1743 edition as On the movement of animals. Berlin: Springer, 1989. 

Digital facsimile of the 1743 edition from the Internet Archive at this link.