MUSCLES OF THE BACK 



415 



ligaments. The aponeurosis covers the muscles of the sacral region and is there imited to 

 the overlying fascia by more or less dense areolar tissue. Opposite the iliac crest fibre-bundles 

 begin to take origin from the lateral margin of the dorsal surface as well as from the deep or 



Fig. 381. — The Fifth Layer of the Muscles of the Back. 



Semispinalis capitis 

 Longissimus capitis 



Seventh cervical vertebra 



Longissimus cervicis 

 Ilio-costalis cervicis 



Longissimus dorsi 

 Ilio-costalis dorsi 



Spinalis dorsi 



_ _ _ Twelfth thoracic vertebra 



nio-costalis lumborum 



Obliquus internus 



Sacrospinahs 



Fifth lumbar vertebra 



ventral surface of the aponeurosis of origin, and gradually the Une of dorsal attachment extends 

 medially untU, in the lower thoracic region, the tendon becomes completely embedded in the 

 muscle-fasciculi which take their origin from it. The aponeurosis, which is the strongest in 

 the lower lumbar region, is composed chiefly of fibres which take a direction upward and some- 

 what lateralward. 



