174 HUMAN PHYSIOLOGY. 



in the opposite side, with a complete preservation of voluntary power 



and of the muscular sense. 



A vertical section through the middle of the gray matter results in the loss 

 of sensation on both sides of the body below the section, but no loss of volun- 

 tary power. 



Paralysis from Injuries 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 urinae, 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, pectmeus, adductor longus, magnus, and brevis, ob- 

 turator, vastus externus and internus, etc. 



At the Upper Limit of the Lumbar Region. Sensation and motion paralyzed 

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

 cular walls of the abdomen, interfering with expiratory movements. 



At the Lower Portion of the Cervical Region. Paralysis of the legs, etc., 

 as in the foregoing; in addition, paralysis of all the intercostal muscles and 

 consequent 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, diffi- 

 culty 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. 



THE MEDULLA OBLONGATA. 



The medulla oblongata is the expanded portion of the upper part of the 

 spinal cord. It is pyramidal in form and measures i J inches in length, 

 f of an inch in breadth, of an inch in thickness, and is divided into 

 two lateral halves by the anterior and posterior median fissures, which are 

 continuous with those of the cord. Each half is again subdivided by minor 

 grooves into four columns viz., ventral, pyramid, lateral and tract olivary 

 body, restiform body, and dorsal pyramid. 



i. The ventral pyramid is composed partly of fibers continuous with those 

 of the ventral column of the spinal cord, but mainly of fibers derived from 

 the lateral tract of the opposite side by decussation. The united fibers then 

 pass upward through the pons Varolii and crura cerebri, and for the 

 most part terminate in the corpus striatum and cerebrum. 



