460 THE RESPIRATORY MECHANISM. 



to, of "sympathetic" fibers in some organs. Having totally dis- 

 connected the suprarenal system (the thyroid, the anterior 

 pituitary, the splanchnics, and the adrenals) from the vaso- 

 motor system, the latter, viewed from our standpoint, merely 

 represents subdivisions of the general motor system at all 

 times. We are, therefore, bound to point to a vasomotor func- 

 tion as an attribute of all motor nerves. Of course, the vaso- 

 motor center being admittedly located in the fourth ventricle 

 and the table just submitted showing that all motor nerves or 

 motor connections are related with the same structure, a step 

 in the elucidation of this point has been made; but we have 

 still to complete the list by showing that even these apparently 

 independent filaments also arise from the medulla or cord. 



The nerves that receive filaments from the sympathetic 

 are the 3d, 4th, 5th, 6th, 10th, and 12th. The 3d, or motor 

 oculi, which supplies several eye-muscles, the circular fibers 

 of the iris, and the ciliary muscle, receives its sympathetic 

 filament from the cavernous plexus. The latter can only be 

 derived in this locality from one of two sources: either the 

 suprarenal system nervous connections or the spinal cord 

 through cervical or dorsal nerves (unless conjoined with the 

 vagal or glosso-pharyngeal roots, which is unlikely). Pupil- 

 dilating fibers were traced by Sherrington, in monkeys, and 

 by Langley, in cats and dogs, in the first and second and to 

 a less extent in the third and fourth dorsal nerves. Onuf and 

 Collins 23 refer to the observations of Miiller in the case of 

 "a man in whom a lesion could be distinctly located in the 

 region of the first and second dorsal nerve-roots, and in this 

 case there was marked contraction of the pupil, ptosis, and 

 sinking in of the eyeball." They state that the results of in- 

 vestigators indicate that the pupil-dilating fibers occur with 

 the greatest constancy in the first dorsal and almost constantly 

 in the second dorsal, and refer to the fact that Salkowski 

 placed the origin of these fibers in the medulla oblongata. 

 Finally they express the opinion that, "although the evidence 

 is preponderatingly in favor of the existence of a cilio-spinal 

 center, yet the question has not been definitely settled." 



The fourth pair, or patheticus, which governs the action 



23 Onuf and Collins: Loc. cit., p. 90. 



