EEPORT ON THE SPHENISCID.^. 117 



Gastrocnemiens, Cuvier, vol. i. p. 383. 



Gastrocnemien, Meckel, vol. vi. p. 103, No. 3. 



Described hy EeiJ, p. 144. 



Gastrocnemius, Owen, p. 37. 



Gastrocnemien and Solaaire tibial, Gervais and Alix, pp. 34 and 35. 



Attacliments. — The gastrocnemius arises by three distinct heads — an outer, an inner, 

 and an anterior. The outer head is attached by means of a strong tendon to a depression 

 on the posterior surface of the femur, immediately above the external condyle. To 

 this tendon is attached the superficial head of origin of the flexor perforatus digi- 

 torum. The inner head arises from a depression on the posterior surface of the femur, 

 immediately above the internal condyle. To this tendon are attached a number of the 

 posterior fibres of the adductor magnus. The inner head, moreover, arises from the 

 postero-internal border of the tibia, close to the attachment of the internal lateral liga- 

 ment of the knee joint to that bone. The anterior head arises from the inner surface of 

 the patella, from half an inch in length of the anterior internal tibial crest, and from so 

 much of the subjacent aponeurosis which separates it from the tibialis anticus as corres- 

 ponds to the upper third of the tibia. The tendon of insertion of the inner head unites 

 with that of the anterior about the middle in length of the tibia, and is joined immediately 

 above the ankle joint by the tendon of insertion of the outer head. After passing behind 

 the ankle joint, the tendo Achillis divides into two slips, of which the outer is inserted into 

 the outer side of the distal extremity of the fourth or external metatarsal bone, whilst the 

 inner is attached to the inner side of the base of the second or internal metatarsal bone. 



Eelati.ons. — The outer head lies at its origin between the insertion of the biceps on its 

 inner, and the superficial origin of the flexor perforatus digitorum on its outer side. As this 

 head passes downwards, it rests upon the deep portion of the flexor perforatus. The 

 inner head at its origin is separated from the anterior head by the insertions of the semi- 

 membranosus and semi-tendinosus, and rests upon the flexor digitorum perforatus. The 

 anterior head rests upon the tibialis anticus above, and on the flexor digitorum perforatus 

 below. Its patellar origin is in part continuous with the insertion of the sartorius. 

 Action. — The muscle flexes the knee and extends the ankle-joint. 

 Nerve supply. — The outer and inner heads are supplied by branches which are given 

 off" from the sciatic nerve above the knee joint. The anterior head is supplied by an 

 indirect branch of the same trunk given off below that articulation. 



Remarks. — Both Tiedemann and Wiedemann describe the gastrocnemius as arising 

 by two heads. From their description, however, it is evident that they regard the innei 

 and anterior heads, as above described, as constituting a single origin. My anterior 

 head is described by Gervais and Alix as a distinct muscle under the name of tibial 

 solaaire. 



