FUNCTIONS OF THE SPINAL CORD. 113 



Throughout the spinal cord are situated numerous centres which preside 

 over the following reflexes, viz. : 



The patellar tendon reflex takes place through the segments from which 

 arise the 2d, 3d and 4th lumbar nerves ; the cremasteric reflex through the 

 segment from which arise the 1st and 2d lumbar nerves; the abdominal 

 reflex through the segments between the 8th and I2th dorsal nerves; the 

 epigastric reflex through the segments from which arise the 4th, 5th and 

 6th dorsal nerves. 



Paralysis from Disease of the Spinal Cord. 



Seat of Lesion. If it be in the lower part of the sacral canal, there is 

 paralysis of the compressor urethrse, accelerator urinse, and sphincter ani 

 muscles ; no paralysis of the muscles of the leg. 



At the upper limit of the sacral region. Paralysis of the muscles of 

 the bladder, rectum and anus ; loss of sensation and motion in the muscles 

 of the legs, except those supplied by the anterior crural and obturator, 

 viz. : psoas iliacus, Sartorius, pectineus, adductor longus, magnus and 

 brevis, obturator, vastus externus and internus, etc. 



At the upper limit of the lumbar region. Sensation and motion para- 

 lyzed in both legs ; loss of power over the rectum and bladder ; paralysis 

 of the muscular walls of the abdomen interfering with expiratory move- 

 ments. 



At the lower portion of the cervical region. Paralysis of the legs, etc., 

 as above ; in addition, paralysis of all the intercostal muscles and conse- 

 quent interference with respiratory movements ; paralysis of muscles of 

 the upper extremities, except those of the shoulders. 



Above the middle of the cervical region. In addition to the preceding, 

 difficulty of deglutition and vocalization, contraction of the pupils, paralysis 

 of the diaphragm, scalene muscles, intercostals, and many of the accessory 

 respiratory muscles ; death resulting immediately, from arrest of respiratory 

 movements. 



Anterior half of spinal cord. Paraplegia developing symmetrically. 



Posterior half of spinal cord. Characteristic symptoms of locomotor 

 ataxia or tabes dorsalis. 



In the gray substance in the vicinity of the central canal and anterior 

 horns. If the lesion be acute, symptoms characteristic of acute spinal 

 paralysis manifest themselves ; if chronic, symptoms characteristic of pro- 

 gressive muscular atrophy. 



