xxiv. 7 LIMBS 635 



The ilium is very broad in man, increasing the surfaces for attach- 

 ment of the glutei, iliacus (a flexor of the hip), and for the abdominal 

 muscles, which are attached along its crest and have an important part 

 to play in carrying the weight of the viscera. 



7. The limbs of man 



Many changes would be needed to convert an ape-like leg and foot 

 to the human condition (Fig. 395). The femur of man is straight and 

 the articular surface at its lower end set at an angle to the shaft. This 

 allows the lower legs and feet to be as nearly as possible below the 

 centre of gravity in standing, in other words, for the knees to be held 

 together although the femoral heads are wide apart. At the ankle joint, 

 on the other hand, the articular surface is at right angles to the tibia in 

 man, at an oblique angle in apes, since in the latter the foot is turned 

 outwards. In ourselves the weight is transferred from the tibia to the 

 talus and then partly backwards to the calcaneum and partly forwards 

 through the tarsus to the metatarsal heads (Fig. 412). The calcaneum is 

 modified for this weight-bearing and the tarsus and digits even more 

 so, the whole foot being converted into an arched system, no trace of 

 which is found in apes. With this arrangement the hallux is not used 

 for grasping and is very large. It is held in line with the other digits and 

 the whole forms a compact wedge with a joint at the metatarsal heads. 

 In walking, when the foot is raised by the calf muscles, the toes remain 

 on the ground, to prevent slipping forwards. The condition in which 

 the first toe is the longest is peculiar to man, but in some monkeys and 

 apes the axis tends to shift from the third digit medially and the 

 human condition is an accentuation of this change, with the metatarsal 

 and first phalanx of the first digit becoming long and strong. Even in 

 modern human populations the second toe as a whole is often longer 

 than the first; this condition was perhaps commoner in historical 

 antiquity (the 'Grecian toe'), and may be a cause of foot trouble, the 

 long second digit being unsuited to the stresses it is made to bear. 



The differences between apes and men in the arms and hands (Fig. 

 410) are marked, though perhaps less striking than in the feet. The 

 human fore-limb is, of course, relatively much shorter than that of any 

 ape and its muscles far less powerful. In order to carry the whole 

 weight of the large body an ape needs enormous muscles all along the 

 limb. Thus the serratus anterior, which pulls the body up on the 

 scapula, is very large and the ribs to which it is attached have large 

 flattened surfaces, are very long, and extend far caudally; the chest of 

 man is much more lightly built. Similarly, the muscles of the shoulder 



