The images show the insertion and branching of nerves in muscles. According to Galen, muscle fibres are in fact nerve fibres, which through their branching and splitting inside the muscles become woven into the muscle flesh. See for example, Galen, On the Motion of Muscles I 1 (3,3—9 Rosa = IV 371—372 K.).
This idea of Galen is discussed in detail in Ezrokhi, D. and Lewis, O., “Galen’s Typology of Organs”, Apeiron, forthcoming 2025.
The images below show the semitendinosus muscle of the pig at the back of a female pig’s hindlimb. The muscle has been cut open to reveal the insertion of the nerve and its branches inside the muscle.
Nerve Fibres inside a Muscle