170 COUES ON THE OSTEOLOGY 



the second of the two femoral " adductors " just described. It crosses obliquely over the 

 coccygeal muscle ; passes outwards and forwards, and is inserted by a narrow flat tendon 

 into the tibia, about an inch below the joint. 



Semi-membranosus. Arises from the pelvis about midway between the acetabulum and 

 tuber ischii, and is inserted by a broad membranous tendon into the crest of the tibia just 

 above the insertion of the preceding. It is a thin flat muscle, with a tendon fully as wide 

 as the fleshy portion. 



These two muscles are the proper flexors of the leg upon the thigh. Their tendons 

 form the " inner hamstrings," and from their situations, relations, and uses are undoubtedly 

 to be homologized with the semi-tendinosus and semi-membranosus. 



In my dissections I failed to detect a "gracilis" muscle; or any connection of a tendon 

 of a crural extensor with a digital flexor, by which flexion of the toes is produced by the 

 mere bending the knee and ankle-joints, as is the case with the Insessores, etc. I do not 

 think that such a mechanism exists, at least to any marked degree, although I may be 

 mistaken. 



Considering collectively the muscles which act upon the thigh and leg, it will be noticed 

 that by far the greater part of their combined force is exerted to produce powerful extension 

 of the thigh and flexion of the leg, with a free rotation of the latter upon the former; while 

 the power of flexion of the thigh, and extension of the leg, is reduced in a proportionate 

 degree. The importance of such a disposition of the muscular forces of the parts to the 

 full development of vigorous natatorial power, is too evident to need comment ; for the 

 bringing forward of the leg requires but very slight effort in comparison with that neces- 

 sary to produce the energetic backward stroke by which the bird is propelled forward. 

 Now, in examining the muscles of the leg and foot, we shall find that they are so disposed 

 as to most effectively continue the powerful backward stroke which began at the hip-joint. 

 The extensors of the metatarsus vastly predominate both in number and size over the 

 flexors. No less than seven tendons pass over the posterior aspect of the tibio-tarsal 

 articulation, while only three are found uj>on its anterior face. I will notice the more im- 

 portant of these muscles. 



Tibialis anticus. Arising from the very tip of the projecting spine of the tibia, and from 

 the whole anterior aspect of that spine down to the joint, it lies aloug the face of the bone 

 for its whole extent, though no more fibres take origin from it. It is fusiform in shape. 

 Its tendon passes directly over the anterior surface of the joint, being bound down by a 

 transverse ligament, and is inserted into the head of the metatarsal bone. It directly 

 flexes the tarsus. 



Extensor dU/Uorum communis. Much smaller than the last, lying beneath and internally to 

 it. It is somewhat penniform in shape, its tendon running up for some distance on its 

 inner edge, its outer surface being covered with dense fascia3. It arises from the anterior 

 aspect of the spine of the tibia, down as far as the knee-joint, for which extent it is inti- 

 mately blended with the muscles by which it is surrounded. After passing the joint, it be- 

 comes distinct from any other muscle ; but fibres continue to take origin from the face of 

 the tibia for nearly its whole length. Its tendon passes behind and internal to that of the 

 tibialis anticus, passes through an osseous canal formed by the bony bridge which stretches 

 across between the malleoli, and runs along the anterior edge of the metatarsal bone, in a 

 deep sulcus; about half an inch from the end of the bone, it gives off the tendon which 

 goes to the inner anterior toe ; this at once divaricates in a special groove, while the tendon 



