The peroneus longus arises from the external tuberosity of the tibia; towards the middle of the leg it is replaced by a tendon. This proceeds towards the tarsus, but previously it passes between the tibia and fibula. In the ox it is situated in front of the coronoid tarsal bone; we recollect that this bone is regarded as representing the inferior extremity of the fibula (see p. 97). Then it passes into a groove belonging to the cuboid bone or to the cuboido-scaphoid bone in the ox, traverses obliquely the posterior aspect of the tarsus, and is inserted into the rudimentary bone which represents the first toe; or, if this does not exist, into the innermost of the metatarsal bones. This muscle is an extensor of the foot. It also rotates it outwards in the animals in which the articulation permits this latter movement. =Peroneus Brevis= (Fig. 83, 8; Fig. 83, 10; Fig. 84, 10; Fig. 86, 6).--In the dog and the cat, this muscle is covered in part by the peroneus longus, and arises from the inferior half of the tibia and the fibula; at the level of the tarsus it becomes tendinous, passes into a groove hollowed out on the external surface of the inferior extremity of the fibula, and terminates on the external aspect of the superior extremity of the fifth metatarsal. A little before this insertion it crosses the tendon of the long peroneal in passing to the outer side of the latter. To the short peroneal muscle is found annexed a very thin fasciculus which lies upon it. This fasciculus arises from beneath the head of the fibula, and is soon replaced by a thin tendon, which, accompanying that of the short peroneal, proceeds towards the foot, after having traversed the groove in the inferior extremity of the fibula; passes along by the fifth metatarsal (Fig. 84, 12); blends at the level of the first phalanx of the fifth toe with the corresponding tendon of the long extensor of the toes, and partakes of the insertions of this tendon. This fasciculus is designated by some authors under the name of the peroneal of the fifth toe, or the proper extensor of the same toe. But what makes still further complications is that other authors regard it as an anterior, or third, peroneal. Now, these names are those which other anatomists have applied to the fasciculus of the anterior tibial, which, in the pig and the ox, is fused in part with the long extensor of the toes. Hence there results a confusion which is truly regrettable. In brief, we can, without inconvenience, consider it as a fasciculus of the short peroneal muscle.