296 



AVES. 



the preceding and situated beneath it, which 

 arises from the outer margin of the ilium, and 

 is inserted into that part of the femur which 

 corresponds to the lesser trochanter, is regarded 

 by Meckel as the Iliacus internus, which Cu- 

 vier states to be wanting in Birds. It is, how- 

 ever, present in most, and is seen highly deve- 

 loped in the Ostrich. 



The muscles analogous to the Pyramidulis 

 and Gemellus superior exist in Birds. 



There are most commonly three adductors of 

 the thigh. The inferior, external, and posterior 

 one arises from the middle of the external sur- 

 face of the anterior margin of the ischio-pubic 

 bone, and is inserted into the greater part of 

 the lower half of the femur at 38. 



The second and third adductors are situated 

 internally to the preceding ; the latter of these 

 may be compared to the Pectineus. 



The Sartorius (39) arises from the anterior 

 point of the ilium, and passes down to be 

 attached to the head of the tibia ; it is an ex- 

 tensor of the leg upon the thigh. 



The Rectus J'emoris (40) arises by a thin 

 but wide aponeurosis from the spines of the 

 sacrum, after a short course it joins the Cruroeus 

 and Vasti (42), and is inserted into the head of 

 the fibula. It corresponds according to Meckel 

 with the Tensor vagina femoris and the Glut<eus 

 magnus. 



The Gracilis (41) arises from the superior 

 part of the pubis, descends along the inner 

 side of the thigh, and towards the lower extre- 

 mity of this part, is continued into a long and 

 strong tendon, which passes in front of the 

 knee-joint, and over the extensor tendon of the 

 leg to the outer side of the fibula, whence it pro- 

 ceeds inwards, anterior to the tendon of the pero- 

 neal flexor, to become united to the outer origin 

 of the flexor perforatus of the toes. Meckel con- 

 siders that the muscle now described represents 

 the Rectus J'emoris of mammalia, and regards 

 as the Gracilis a small and thin muscle, whose 

 origin has been transferred lower down, from the 

 pubis to the femur, from the internal side of 

 which it passes to the internal and superior part 

 of the tibia. Be this as it may, the disposition 

 of the former muscle is such, passing, viz. first, 

 over the convexity of the knee-joint, and after- 

 wards over the projection of the heel, that from 

 its connection with a flexor of the toes, these 

 must necessarily be bent simultaneously with 

 every inflection of the joints of the knee and 

 ankle. As these inflections naturally take 

 place when the lower extremities yield to the 

 superincumbent weight of the body, birds 

 are thus enabled to grasp the twigs on which 

 they rest whilst sleeping, without making any 

 muscular exertion. 



There are three flexors of the leg : one (43) 

 which, although single, is from its insertion 

 into the back of the fibula, analogous to the 

 "Biceps flexor cruris of the human subject : ano- 

 ther on the inside is attached to the tendon of 

 the extensors of the foot as well as the tibia ; 

 this muscle might be called the Semvmembranosus 

 (44) : the third Jlr.ror is in the middle (45), 

 it comes from the ischium, and as it descends 



it receives a broad fleshy slip from the back of 

 the femur. It is inserted on the back of the 

 tibia, the tendon covering those of the extensors 

 of the heel. 



The muscles of the feet present in Birds 

 essential resemblances to the same parts in 

 Reptiles. They are divided into muscles of 

 the tarsus, of the metatarsus, and of the toes, 

 the latter being subdivided into long and short. 

 The principal points in which they differ from 

 the same muscles in Reptiles and the Mammalia 

 are the following: their origins and carneous 

 portions are not situated on the foot but higher 

 up on the tibia and even on the femur. The 

 great length of the metatarsus occasions the 

 smaller muscles to be of a greater proportional 

 length than in other animals. The muscular 

 portions are most developed in the Raptores, 

 Scansores, and Natatores ; the Insessores and 

 Rasores present an intermediate proportion ; 

 the Cursores and Grallatores have the longest 

 tendons. 



The Gastrocnemius (46) has three distinct 

 origins : two of these are superficial, one from 

 the outer, the other from the inner condyle of 

 the femur; the third origin is lower down from 

 the inner side of the tibia and fibula (47). 

 They unite to terminate in a thin and broad 

 aponeurosis, which after becoming closely con- 

 nected with a fibro-cartilage appertaining to the 

 flexor digitorum, proceeds to be inserted into 

 both the outer and inner margins of the tarso- 

 metatarsal bone. 



The Tibiulis anticus (48) arises from the an- 

 terior part of the upper extremity of the tibia, 

 below which its tendon passes through an 

 aponeurotic loop extended from the outer to 

 the inner margin of the tibia. It has also a 

 second origin, by means of a slender tendon, 

 from the anterior part of the external condyle 

 of the femur. It is generally inserted pretty 

 high up into the tarso-metatarsal bone between 

 the outer and inner margins ; but in the Psit- 

 tucldce. it is attached lower down to the internal 

 border, so as to turn the foot inwards as well as 

 raise it, a disposition which is extremely favor- 

 able for the act of climbing. 



The Peroneus (49) is a much smaller muscle ; 

 it extends from the lower region of the fibula, 

 and the outer and anterior edge of the tibia to 

 the tarso-metatarsal bone, into the outer side of 

 the base of which it is inserted. 



The Flexor perforatus sen longus digitorum 

 (50) forms the superficial and external mus- 

 cular mass of the leg : it arises by one mass 

 from the posterior part of the external side of 

 the femur, immediately in front of the outer 

 head of the gastrocnemius ; another portion 

 arises from the outside of the lower extremity 

 of the femur ; these two heads unite below the 

 middle of the leg and constitute one fleshy belly 

 which gives off three tendons ; these proceed to 

 the proximal phalanges of the three outer toes 

 where they bifurcate to give passage to the ten- 

 dons of ihejlexor perforans. 



The Flexor pollicis (51) arises, by its anterior 

 head, from the anterior and upper part of the 

 tibia, and by its posterior head from the ex- 



