THE INNERVATION OF THE LUNGS. 401 



of the superior oblique muscle, also receives filaments from 

 the cavernous plexus of the sympathetic; hence its connection 

 with the medulla through dorsal nerves is as likely as in the 

 case of the third nerve. The fifth pair, or trigeminal, receives 

 its sympathetic filaments from the carotid plexus: that con- 

 nected with the anterior pituitary lobe. Examination of this 

 communication, however, shows that the cavernous plexus is 

 the nearer one, and that the connections with it are direct 

 by two decussating embranchments. Though there would be 

 no difference as to its functional isolation and its probable 

 connection with the medulla, except if electricity be used, 

 were its fibers conjoined to those of the carotid plexus (dif- 

 ferent nerves often following the same path), it is probable 

 that the sympathetic filaments to the third pair are connected 

 with the cavernous plexus, and that they are also, therefore, 

 of medullary origin. The sixth, or abducens, is also stated 

 to receive its sympathetic filaments from the carotid plexus 

 through the Vidian, but again is it found on examination that 

 the Vidian is connected, not with the carotid plexus, but 

 primarily through a branch which in turn decussates from the 

 main trunk, the so-called superior ganglion of the sympa- 

 thetic, from which also originates the cavernous plexus. The 

 twelfth, or hypoglossal, receives its sympathetic branch from 

 a spot below this and evidently from the same trunk. Hence 

 the 4th, 5th, 6th, and 12th may be said to be traceable to a 

 common and adjoining source through the original source 

 of the cavernous plexus: i.e., the cord. Finally the tenth, or 

 pneumogastric, receives the three cardiac "sympathetic" nerves, 

 which contribute to the formation of the cardiac plexus. The 

 origin of these nerves and their motor functions we have 

 already reviewed. 



All these facts seem to us to completely establish the gen- 

 eral motor system as a functional entity, and to centralize in 

 the medulla and the cord all the sources of functional motor 

 activity that depend upon nervous impulses. Inasmuch as it 

 includes within its manifestations of activity all vasomotor 

 functions, it seems clear to us that to remove or destroy this 

 vasomotor area means simply to remove or destroy what we 

 may call for the time being the centers of functional activity 



