REPORT ON THE SPHENISCID.E. 119 



Attachments. — The peroneus brevis is a very slender muscle. It arises from the upper 

 two-thirds of the anterior surface of the shaft of the fibula, from a corresponding extent of 

 the adjacent border of the tibia, and from the interosseous membrane. Its tendon passes 

 obliquely downwards and backwards, and after crossing the outer side of the ankle joint, 

 is inserted into the posterior surface of the upper end of the fourth or external meta- 

 tarsal bone. 



Action. — This muscle flexes the ankle joint. 



Relations. — The origin of the peroneus brevis lies in contact with, and separates the 

 fibular origin of the peroneus longus from the tibialis anticus. As its tendon crosses the 

 ankle joint it is concealed by that of the peroneus longus. 



Nerve supioly. — A branch from the anterior tibial nerve. 



Remarks. — Meckel rightly observes that this muscle is extremely feeble in the 

 Penguins as compared with other birds. 



4. Plantaris. 



La grele plantaire, Vicq d'Azyr, 1774, p. 512, Xo. 2. 



Muscle No. 4, Meckel, vol. vi. p. 106. 



Described by Eeid, pp. 144 and 145. 



Soleus, Owen, p. 38. 



Jambier posti'rieur, Gervais and Alix, p. 35. 



Attachments. — The plantaris is a slender muscle. It arises from about one inch in 

 length of the postero-internal border of the tibia, immediately below the upper end of 

 that bone. The muscular fibres opposite the junction of the upper and middle thirds of 

 the tibia give place to a tendon which is inserted into the upper border of the fibro- 

 cartilage behind the ankle joint. 



Action. — Inasmuch as the fibro-cartilacre into which this muscle is inserted is attached 

 by its lower border to the upper ends of the metatarsal bones, the plantaris will extend 

 the foot at the ankle joint. 



Relations. — The belly of the muscle lies immediately behind the internal lateral 

 ligament of the knee joint, and rests against the inner border of the tibial, head of the 

 flexor perforans digitorum. Close to its insertion its tendon is crossed superficially by 

 the tendon of insertion common to the inner and anterior heads of the gastrocnemius. 



Nerve supply. — A branch of the sciatic nerve. 



yd) Muscles inserted into the Phalanges. 

 1. Muscxdus ambiens. 



Crural grele, Vicq d'Azyr, 1774, p. 507, No. 1. 



Der schlanhe Schenkelmuakel, Wiedemann, p. 97. 



Der schlanke SchenJcel-lIuskel, Tiedemaun, p. 332, No. 3. 



