MUSCULAR SYSTEM. I/-") 



their prey, or to strike it to the ground, and they assist in 

 bending forwards the trunk in striking, by their large recti 

 abdominis, which here extend forwards to the anterior end of 

 the sternum. The great extent of the fleshy part of their 

 diaphragm aids their rapid and extensive respiration. The 

 central tendinous portion of the diaphragm is much more ex- 

 tensive, and consequently the muscular part less, in the ru- 

 minating and other herbivorous quadrupeds. The muscles 

 of the lower jaw in the cheiroptera and the levators of the 

 upper lip are generally strong, as in the carnivora, and most 

 of them are nocturnal predaceous animals, but as they pursue 

 their prey through the air, the muscles proceeding from their 

 scapula, their clavicle, and their sternum, to the humerus are 

 of great size and strength, and the flexors of their carpus 

 and fingers send down very long and thin tendons to the 

 lengthened phalanges of the fingers, so as to lighten the dis- 

 tal extremities of the hands, and to adapt them for progres- 

 sion through so rare a medium. The quadrumanous animals 

 being organized for a semi-erect position, and climbing move- 

 ments, have the flexor muscles strongly developed on all 

 their extremities, and the lengthened form and feebleness of 

 the extensors of their posterior extremities, as the glutei 

 muscles, the recti femor is ^ the vasti, the gastrocnemii, and 

 other extensors, so large in the human body, produce that 

 smallness of the nates, the thighs, and the calfs, so charac- 

 teristic of this climbing frugivorous order. The muscles of 

 the jaws and of the neck are strongest in the baboons, 

 where the trunk is most adapted for the horizontal posture, 

 and the ferocity and general strength are almost those of 

 carnivora. The flexors of the coccygeal vertebrae are most 

 powerful in the long prehensile tail of the aides, or spider- 

 monkeys of America, in which the long recti abdominis are 

 still destitute of tendinous intersections, as in many of the 

 inferior mammalia. From the vertical position of the human 

 trunk on the posterior extremities, and the freedom and 

 flexibility of the arms the extensor muscles are most deve- 

 loped on the legs, and the flexors on the arms. The muscles 

 also which support and move the spine, and those which 

 embrace the visceral cavities, are proportionally strong in 

 man, (Fig. 79.) The numerous flexors of the toes are here 

 powerful, to enable the foot to sustain the weight of the 



