1040 BR. p. CHALMERS MITCHELL ON THE 



h;is the practical advantage that the anatomist gains, at least 

 tempovaTily, a useful dexterity in exposing the structures on 

 which he is engaged and is able to cover much ground in a 

 relatively short space of time. 



After giving an accovint of the muscles in a generalized tj'^pe, I 

 shall proceed to a systematic description of the conditions presented, 

 following the classification given by Dr. Gadow in the article 

 Bird, in the Eleventh Edition of the Encyclopaedia Britannica, 

 and finally shall discuss some of the problems suggested by the 

 degree of coincidence between the vaiying conditions of these 

 muscles a.nd a classification which is based on other anatomical 

 facts. 



The Peroneal Muscles in Chauna chavaria (text-fig. 179). 



In some respects the Screamers are generalized birds with 

 aftinities pointing in many directions, and it happens that the 

 condition of the peroneal muscles in other birds can be easily 

 described as specializations of the Screamer condition chiefly by 

 loss of parts. 



Feroneus superficialis sen longtts. — This is the most superficial 

 mass of muscle seen when the skin is removed on the outer, upper 

 aspect of the leg from the knee downwards. Its very large fleshy 

 mass arises from the anterior and lateral crista of the tibia, from 

 the head of the fibula and partly from the fascia covering the 

 knee. Laterally, where it is bounded by the external head of the 

 gastrocnemius on the one side, and the tibialis anticus on the 

 other, its fasciae are closely attached to the fasciae of these muscles. 

 The muscular mass is roughly triangular, and from the broad 

 base at its origin from the upper end of the tibia and fibula, 

 it converges to a flat tendon which is apparent about three 

 quarters way down the leg and rather more on the outer than the 

 anterior aspect. There is a deep origin formed by a comb of 

 fibres projecting inwardly as a keel along nearly the whole length 

 of the triangular portion of the muscle and arising partly from 

 the whole length of the fibula and partly from the tibial surface 

 immediately under the fibula. When the tendon has nearly 

 reached the tarsal joint, it gives off" a very broad and strong anchor 

 (text-fig. 179, Anch.) to the cartilaginous sustentaculum which is 

 pierced by some of the flexor tendons and joined superficially by 

 the gastrocnemius tendon. It is then continued outwards and 

 downwards across the ankle-joint, immediately under the skin, 

 but running through a synovial membrane which has to be cut 

 open to expose it fully, and ultimately, about a quarter of the 

 distance down the tarso-metatarsal shaft, it fuses with the flexor 

 tendon of the third digit (flexor primus sen jDcrforatus III) (text- 

 fig. 179, P.L. Ill), It is supplied by a branch of the ischiadic 

 nerve. 



The function of this muscle is to straighten the tarsus meta- 

 tarsus on the tibio-taisus and then to flex the third toe. When 



