line 



AXIAL MUSCLES. 



437 



.e of the centre of gravity the flexion of the joints ceases, the muscles relax, and the limb 

 gradually returns to the ground. The other limb then passes through the same cycle, the weight 

 of the body now resting on the limb which is in contact with the ground. As the foot reaches 

 the ground it, as it were, rolls over it ; the heel touches it first, then the sole, and lastly, as the 

 . foot leaves the ground again, only the toes. In running, the previous events are all exaggerated. 

 The time of the event is diminished, while the force and distance are increased. Both feet are off 

 the ground at one time ; the action of flexors and extensors alternately is much more powerful, so 

 that on the one hand the knees are drawn upwards to a greater extent in the forward movement, 

 and not the whole foot, but only the toes reach the ground in the extension of the limb. The 

 attempt is made to bring the foot to the ground in front of the line of the centre of gravity. At 

 the same time the trunk is sloped forwards much more than in walking. In leaping, the actions 

 of the limbs are still more exaggerated. The movements of flexion of the limb are still more 

 marked, and the foot reaches the ground still farther in front of the line of the centre of gravity. 



RECTUS ABDOMINIS 



AXIAL MUSCLES. 

 THE FASCIAE AND MUSCLES OF THE BACK. 



THE FASCIAE OF THE BACK. 



The general fascial investments of the back have been described along with the 

 superficial muscles associated with the shoulder -girdle (p. 365). The latissimus 

 dorsi muscle has been described as arising in large part from the posterior layer of 

 the lumbo-dorsal fascia. This is a strong fibrous lamina which conceals the sacro- 

 spinalis muscle. 

 In the loin it 

 extends from the 

 spines of the 

 lumbar vertebrae, 

 laterally, to the 

 interval between 

 the last rib and 

 the iliac crest, 

 where it joins the 

 middle layer. 

 Below the loin 

 the posterior layer 

 of the lumbo- 

 dorsal fascia is 

 attached to the 

 iliac crest, and 

 more medially 

 blends with the 

 subjacent tendin- 

 ous origin of the 

 sacrospinalis. 

 The layer can be 

 followed upwards 



Middle layer of lumbar fascia 

 the Sacro- ILIOOOOTALIS 



spinalis in the 

 region of the 

 thorax, where it 

 is attached later- 

 ally to the ribs and is continuous with the intercostal aponeuroses. In the lower 

 part of the thorax it is replaced by the muscular slips of the serratus posterior 

 inferior ; in the upper part of the thorax it passes beneath the serratus posterior 

 superior and blends with the deep cervical fascia. 



Fascia Lumbodorsalis. The lumbo-dorsal fascia consists of three fascial 

 strata, called respectively the posterior layer, just described ; the middle, and the 

 anterior layers. They unite at the lateral margin of the sacrospinalis muscle to 



29 a 



OBLIQUUS EXTERNUS 



ABDOMINIS 

 OBLIQUUS INTEKNUS 



ABDOMINIS 

 TRANSVERSUS 



ABDOMINIS 



Fascia transversalis 

 Peritoneum 



Colon 



Extraperitoneal 

 tissue 



Kidney 



Lumbo-dorsal fascia 



LATISSIMUS DORSI 



QUADRATUS LUMBORUM 



Psoas fascia 



Second lumbar 

 vertebra 



: PSOAS MAJOR 



Anterior layer of 

 lumbar fascia 



MULTIFIDUS 



SEMISPINALIS 

 DORSI 



Vertebral aponeurosis 



LONGISSIMUS DORSI 



FIG. 390. TRANSVERSE SECTION THROUGH THE ABDOMEN, OPPOSITE THE 

 SECOND LUMBAR VERTEBRA. 



