

598 MR. J. C. GALTON ON THE MYOLOGY OF 



The muscles which arise from the extensor surface of the leg in Orycteropus are well 

 marked off into three distinct groups, each of which passes under a strong ligamentous 



pulley peculiar to it. 

 The tibial group comprises muscles proper to the hallux ; such are the extensor pro- 



jh-ihs of this digit, and the tibialis anticus. 



The middle group includes but the four tendinous offsets of the extensor communis, 

 while under the group on the fibular side are comprised the peroneal muscles. 



JPeronei. — These muscles are so blended together at origin that it is not easy to isolate 

 t hem for description. They arise along the outer edge of the fibula, in close company 

 with the extensor communis, from the inward-looking aspect of the bead of tbe bone, and 

 from the external lateral ligament and outer semilunar cartilage. 



Just above the outer malleolus, they become tendinous ; and tbeir tendons, four in 

 number, are kept in place behind this strongly projecting process by a ligamentous band 

 or pulley. 



The most anterior at origin passed over the extensor brevis digitorum to join the expan- 

 sion of the common extensor, at the base of the proximal phalanx of tbe fourtb digit, 

 sending off also a slight slip to terminate in like manner at the little toe. 



A second passed to the outer side of the base of the proximal phalanx of the fifth digit, 

 joining here the metatarso-phalangeal expansion of the common extensor tendon. 



Another terminated at a very strong tubercle developed on the outer side of the base 

 of the metatarsal bone of the same disdt. 



The two last-described muscles seem to answer tolerably fairly to the peronei tertius 

 jmd brevis of human anatomy, respectively. 



The first muscle seems to answer very fairly to one described by Mr. Mivart and Dr. 

 Murie, in their paper on the " Anatomy of the Crested Agouti " \ as the peroneus quarti 



digiii ; or it may be regarded as the muscular resultant developed by the fusion of this 

 with the peroneus quinti digiti. 



The tendon of the homologue of the peroneus longus passed over a groove in a tubercle 

 situated on the outer side of the head of the os calcis, and, on gaining the sole, took a 



turn at a right angle, and passed under the strong plantar ligaments to its usual inser- 

 tion at the fibular side of the base of the metatarsal of the hallux. Soon after its 

 entrance into the sole, it detached, as described by Prof. Humphry 2 , an offset from its 

 anterior edge, which was inserted into the tibial side of the metacarpal of the fifth digit. 

 Record of a similar arrangement will be found in my paper on the myology of Dasypus. 



No reference to this important point has been given, as far as I am aware, either by 

 Meckel or by Cuvier. 



Such a disposition of the tendon of the peroneus longus as that just described 

 obviously ensures the simultaneous adduction, towards the middle line of the foot, of 

 the hallux and fifth digit. 



Tibialis anticus.— A strong, well- developed muscle, arising from the arch formed by 

 the junction of the tibia and fibula at their upper part— also by a small slip from the 



of the former bone, just below the insertion of the patellar ligament— in 



' Proc Zool. Soc. June I860. 



2 



Loc. cit. p. 319. 



