644 NERVOUS SYSTEM. 



interesting feature in one of the cases was the fact that an operation upon the eyelid of 

 the affected side was performed without the slightest evidence of pain on the part of the 

 patient. 



Cases of paralysis of the fifth in the human subject in the main confirm the 

 results of experiments upon the inferior animals. In all the cases in which the fifth 

 nerve alone was involved in the disease, without the portio dura of the seventh, there 

 was simply loss of sensibility upon one side, the movements of the superficial muscles 

 of the face being unaffected. When the small root was involved, the muscles of masti- 

 cation upon one side were paralyzed ; but, in certain cases in which this root escaped, 

 there was no muscular paralysis. The senses of sight, hearing, and smell, except as they 

 were affected by consecutive inflammation, were little if at all disturbed in uncompli- 

 cated cases. The sense of taste in the anterior portion of the tongue was perfect, 

 except in those cases in which the seventh, the chorda tympani, or the lingual branch 

 of the fifth after it had been joined by the chorda tympani, was involved in the disease. 

 In some cases, there was no alteration in the nutrition of the organs of special sense ; 

 but in this respect the facts with regard to the seat of the lesion are not so satisfactory 

 as in experiments upon the lower animals, it being difficult, in most of them, to limit 

 the exact boundaries of the lesion. 



Pneumogastric^ or Par Vagum Nerve. (Second JDivision of the Eighth 



Nerve) 



Of all the nerves emerging from the cranial cavity, the pneumogastric, the second 

 division of the eighth pair, presents the greatest number of anastomoses, the most 

 remarkable course, and the most varied and interesting functions. Arising from the 

 medulla oblongata by a purely sensory root, it communicates with at least five motor 

 nerves in its course, and it is distributed largely to muscular tissue, both of the voluntary 

 and the involuntary variety. Finally, there is no nerve that has been the subject of 

 such extended and elaborate anatomical and physiological investigations, and none, 

 concerning the properties and exact functions of which there has been so much differ- 

 ence of opinion. 



We shall have to treat of the influence of the pneumogastric upon the act of degluti- 

 tion, the heart and circulatory system, the respiratory system, the stomach, the intestines, 

 and various glandular organs. An indispensable introduction to this study is a descrip- 

 tion of its physiological anatomy. 



Physiological Anatomy of the Pneumogastric Nerte. The apparent origin of the 

 pneumogastric is from the lateral portion of the medulla oblongata, just behind the 

 olivary body, between the roots of the glosso-pharyngeal and of the spinal accessory. 

 The deep origin is mainly from what is sometimes called the nucleus of the pneumogas- 

 tric, in the inferior portion of the gray substance in the floor of the fourth ventricle. 

 The course of the fibres, traced from without inward, is somewhat intricate. 



The deep origins of the pneumogastric and glosso-pharyngeal nerves appear to be, in 

 the main, identical. Tracing the filaments from without inward, they may be followed 

 in four directions. The anterior filaments pass from without inward, first very superfi- 

 cially and directed toward the olivary body, but, turning before they reach the olivary 

 body, they pass deeply into the substance of the restiform body, in which they are lost. 

 The posterior filaments are superficial, and they pass, with the fibres of the restiform 

 body, toward the cerebellum. Of the intermediate filaments, the anterior pass through 

 the restiform body, the greatest number extending to the median line in the floor of the 

 fourth ventricle. A few fibres are lost in the middle fasciculi of the medulla, and a few 

 pass toward the brain. The posterior intermediate filaments traverse the restiform 

 body to the floor of the fourth ventricle, when some pass to the median line, and others 



