484 APPLIED ANATOMY. 



dorsal vertebra add three. The lower part of the eleventh dorsal spinous process 

 and the space below it are opposite the lower three lumbar segments. The ^ twelfth 

 dorsal spinous process and the space below it are opposite the sacral segments." The 

 spinal cord ends at the lower part of the first lumbar vertebra. 



The areas of cutaneous sensibility aid in determining the seat of the lesion. The 

 nerves supplying these various areas are shown in Fig. 486. 



Lesions above the fourth cervical nerve 'are very speedily fatal. The muscular 

 paralyses, as guides to the seat of the lesion in the cervical region, are given by 

 Thorburn as follows: 



Supraspinatus and infraspinatus \ p ourt h ce rvical nerve. 



Teres minor (?) / 



f Biceps 



1 Brachialis anticus 



Deltoid . . . 

 Supinator longus 

 Supinator brevis (?) 

 Subscapularis 

 Pronators . 

 Teres major . 

 Latissimus dorsi . 



Fifth cervical nerve. 



Sixth cervical nerve. 



Pectoralis major 



( Triceps . 



\ Serratus magnus 



Extensors of the wrist Seventh cervical nerve. 



Flexors of the wrist Eighth cervical nerve. 



Interossei . . . . . . 1 First dorsal nerve. 



Other intrinsic muscles of the hand j 



In fractures of the dorsal region Thorburn has shown that the lesion is usually 

 two vertebra higher than the nerve coming out from below the displaced vertebra. 

 They cause paralysis of the abdominal muscles, legs, bladder, and rectum. 



According to Starr, fractures in the region of the last two dorsal vertebrae cause 

 anaesthesia up to Poupart's ligament, and if the patient recovers the thighs remain 

 paralyzed. In fractures of the upper part of the lumbar region the paralysis may be 

 limited to the legs below the knees but involves the bladder and rectum. Recovery 

 leaves the patient with some power of getting about on crutches with the aid of 

 apparatus to keep the ankles and knees firm, as the thighs are under voluntary 

 control. 



Lesions below the first lumbar, those of the cauda equina, give paralysis of 

 the feet and peronei, loss of control of the bladder and rectum, and anaesthesia in the 

 saddle-shaped area on the buttocks, about the anus, and on the posterior part of the 

 genitals. 



The diagnosis between lesions of the cauda equina and lower portion of the cord 

 is not always possible. The prognosis of lesions of the cauda equina is, of course, 

 much better than when the cord itself has been injured. 



SPINAL MENINGES. 



The cord is covered by a continuation downward of the cerebral meninges. It 

 has a dura mater, arachnoid, and pia mater. 



Dura Mater. The outer or endosteal layer of the cerebral dura mater ends 

 posteriorly at the edge of the foramen magnum but anteriorly at the third cervical 

 vertebra. The inner or meningeal layer continues downward as a tough fibrous tube 

 from the foramen magnum to the second or third sacral vertebra, and thence is pro- 

 longed downward as a fibrous cord (coccygeal ligament) to be attached to the peri- 

 osteum over the coccyx. The dura mater in the spine does not, as in the skull, act 

 as a periosteum. The vertebrae have a separate periosteum in addition. Between the 

 dura mater and the bodies of the vertebrae is a somewhat loose space filled with fat, 

 fibrils of connective tissue, and a venous plexus. In injuries these vessels are ruptured 

 and bleed and give rise to clots; the blood, however, does not get inside the mem- 

 branes and the effusion rarely assumes a sufficient size to produce compression of the 

 cord. These veins pierce the ligamentum subflavum and thus communicate with 



