SPINAL ACCESSORY. 167 



anatomy as it appears from late researches, and will begin 

 its physiological history with the comparatively recent ex- 

 periments which have advanced our positive knowledge of 

 its properties. 



Physiological Anatomy. The origin of this nerve is 

 very extensive. A certain portion arises from the lower 

 half of the medulla oblongata, and the rest takes its- origin 

 below, from the upper two-thirds of the cervical portion of 

 the spinal cord. That portion of the root which arises from 

 the medulla oblongata is called, by the French, the bulbar 

 portion, the roots from the cord constituting the spinal por- 

 tion. Inasmuch as there is a marked difference between the 

 functions of these two portions, the anatomical distinction 

 just mentioned is important. 



The superior roots arise by four or five filaments from 

 the lower half of the medulla oblongata below the origin 

 of the pneumogastrics. These filaments of origin, in prep- 

 arations hardened by prolonged immersion in alcohol, are 

 shown to be connected with the lateral portion of the me- 

 dulla, and not with the posterior columns. Their origin 

 seems, therefore, to be from the motor tract. 1 



The spinal portion of the nerve arises from the upper 

 part of the cervical division of the spinal cord, between the 

 anterior and posterior roots of the upper four or five cervi- 

 cal nerves. The filaments of origin are from six to eight in 

 number. The most inferior of these is generally single, the 

 other filaments being frequently arranged in pairs. These 

 take their origin from the lateral portion of the cord, rather 

 nearer the posterior median line than the roots from the 

 medulla oblongata. 



Following the nerve from its most inferior filament of 

 origin upward, it gradually increases in size by union with 

 its other roots, enters the cranial cavity by the foramen 

 magnum, and passes to the jugular foramen, by which it 



1 SAPPEY, Traite tfanatomie descriptive, Paris, 1852, tome ii., p. 298. 



