Caninus muscle

The canine muscle (M. caninus) is called in Men 'levator anguli oris'. In most Mammals, it acts more on the wing of the nose than on the angle of the mouth or the upper lip. It covers the canine fossa and has, except in Equidae, remarkable relations with it.

Conformation: Nothing is more variable than this muscle: short quadrangular fleshy sheet in Men, it is in Dogs a large strip broadened rostrally and not very distinct from the levator labii superioris . It is weak in Equidae, where it starts by a short tendon and broadens rostrally. Nearly entirely aponevrotic in Rabbits, it is divided in this species into two beams that diverge towards the nose for the first and towards the upper lip for the other. It reaches its maximal development in Ruminants and Pigs. In these species, it is divided into several conical fleshy beams (three in Ruminants, two in Pigs) that diverge rostrally and are each continued by a tendon; the most ventral of these divisions is described as a distinct muscle, called the depressor labii superioris

Insertions: The canine muscle takes origin on the maxillar, on the caudal border of the canine fossa, a bit ventrally and more or less caudally to the infra-orbital foramen. In carnivorous, this attach merges with the one of the levator labii superioris. The origins of the two muscles are still adjacent, immediately above the facial tubercule of the Bull, between it and the infra-orbital border in Pigs. In Horses and in Men, the origin is located beneath the infra-orbital foramen, a bit rostrally to the facial tubercle. The end is attached to the deep surface of the skin: in Men, above the angle of the outh; in Carnivorous and Equidae, of the upper lip and wing of the nose. In Bulls and Pigs, the dorsal tendon(s) go to the wing of the nose and on the side of the muzzle or the groin; the tendon of the ventral part (depressor labii superioris) goes to this lip. It is more or less the same in Rabbits.

Functions: elevator of the angle of the mouth in Men, the canine muscle participates rather in domestic animals to pull the upper lip and the wing of the nose aside, helping in this way the nostril's dilatation. In Ruminants and Porcines, its ventral beam becomes even a real depressor of the lower lip, that it pulls aside aswell as the muzzle or the groin.