Jan. 8, 1874J 



NATURE 



187 



In all beasts, as in man, the motion of the leg on the 

 foot takes place by means of a joint between the shin- 

 bone of the leg and the small bones of the ankle ; and 

 though in some beasts (as in the orang) there is consider- 

 able power of motion between the first and the second 

 row of ankle bones ; this is small compared with the 

 mobility of the foot and ankle taken together, upon the leg 



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Fig. 5S. Fig 59 



Fig. 58. — Anterior muscles of the Trunk the pectorahs m^jor of the right 

 side and the left external oblique being remo\ed i pectoralis major ; 

 2, pectoralis minor ; 3, subclavius 4, serratus magnus . 5, internal in- 

 tercostals : 6, external oblique ; 7, internal oblique: 8, linea alba. 

 Fig. 59. — Deeper Abdominal Muscles-the external oblique being removed 

 from the left side of the body, and the internal oblique and part of the 

 rectus also, from its right side, i, the internal oblique: its outer ten- 

 djn {2) is cut and reflected from the outside of the rectus to show its 

 deeper tendon (3), which passes within the rectus except towards the 

 pubis ; 4, transversalis : 5, its fascin ; 6, sheath of the rectus — near the 

 pubis, the conjoined aponeuroses of the abdominal muscles pass in front 

 of that muscle ; 7, pyramidalis : 8, rectus of left side, showing the ten- 

 dinous intervals, or llnciE transvcrscc. 



In all birds, on the contrary, not only is there no motion 

 between the ankle-bones (as a whole) and the shin-bone, 

 but the two rows of ankle-bones actually anchylose re- 

 spectively with adjacent parts- the row nearer the leg 

 coming to form one with the shin-bone ; the second row 

 coming to form one with the bones of the foot. Thus in 

 birds the motion of the foot on the leg takes place not 



Fig. 60.— Superficial Muscles of the Perch. The fin-rays of all the fins are 

 cut off. I, great lateral muscle, showing the munerous vertical tendi- 

 nous intersections shghtly but variously inflected ; 2, small superficial 

 muscles inserted into the fin-rays of the dorsal and ventral fins ; slender 

 longitudinal muscle running (in the interval of the summits of the two 

 great lateral muscles) between the dorsal and caudal fins ; 5, similar 

 muscle on the ventral margin, which also appears between the anal and 

 ventral fins : 6, small radiating muscles of the caudal fin : 7. part of the 

 great lateral muscle inserted into the skull : 8 and 9, elevators of the 

 operculum ; 10, elevator 0/ the palato-quadrate arch ; 11 and 12, muscu- 

 lar mass by which its contraction closes the jaws : 13, superficial muscles 

 of the pectoral fin ; 14 and 15, muscles of the ventral fin. 



between the ankle and the shin-bone but between the two 

 rows of ankle-bones. 



The same thing to a less degree takes place in reptiles ; 

 the ankle-bones do not indeed anchylose with the shin- 

 bone and foot respectively, but they nevertheless unite 

 with those parts so firmly that motion takes place between 



the bones of the ankle and not between the whole ankle 

 and the leg. 



Now in the frog's class, e.g. in the order Urodcla, we 

 meet with a condition which is mimmahan rather than 

 reptilian or avian. Motion t.ikes place freely between the 

 leg and the whole tarsus. Moreover, the number and 

 proportions of the ankle-bones themselves far more 

 closely agree with the condition of the same parts exhi- 



Fig. 61.— Superficial Muscles of Extensor Side of Leg and of parts of 

 Trunk and Tail of Menopoma. ES^ erector spinse — directly continued 

 into dorsal half of tail : ELD, extensor longus digitorum pedis ; /"C, 

 femoro-caudal ; GMx, probably rectus femoris : /, muscle resembling 

 i iacus ; ILC. iiio-caudal : IF, ilio-peroneal : RF.\>yc\. of great exten- 

 sor of thigh; SM and ST, muscles like the semi-membranosus and 

 semi-tendinosus. 



bited to US by certain beasts than it does with that which 

 is possessed by any bird or of most reptiles. 



The frogs and toads, however, differ from the Urodela 

 and present us with a peculiar condition of the ankle- 

 bones, in that the two which represent the bones of the 

 first row are so greatly elongated as to give to the limb an 

 additional segment — as it were two " long bones" more. 



We should search in vain through every other order of 

 the Batrachian class, through every known group of birds 

 and reptiles, both living or fossil, to find any analogous 

 structure. None of the lowest mammals, no marsupial, no 

 rodent, no insectivorous or carnivorous beast, no. hoofed 

 mammal, presents us with anything of the kmd. Never- 

 theless, at almost the other end of the series, in the very 



Fig. 6j. -Diagram of Caudal Muscles of Right Side 01 Tail of Iguana, 

 showing how the ventral mass resembles the dorsal part, and how the 

 tendinous intersections of the muscular fibres are drawn out into cones. 

 N, neural spine : H, hypapophysial spine ; ::, zygapophysis ; /, trans- 

 verse process ; r, dorsal series of cones ; 2, upper lateral series of cones 

 3, lower series of cones : ventral series of cones. 



highest order, that to which man himself belongs, we 

 acmally find a very similar development. 



Amongst the very peculiar beasts which inhabit the 

 island of Madagascar, there are certain small creatures, 

 " Half-Apes," belonging to the genus Cheirogalcus, in 

 which two of the ankle-bones are elongated in a manner 

 similar to that of the frog. The same character is more 

 marked in an African genus of half-apes {Galago), and 

 still more so in a third half-ape {Tarsius), from the island 

 of Banca. Now it is absolutely impossible to believe that 

 a special genetic affinity connects together by a peculiarly 



