S2 THIRD UEPORT — 1833. 



after its section in an ass*, and that side of the face remained 

 at rest and placid during the highest excitement of the other 

 parts of the respiratory organs." These and similar observa- 

 tions are all consistent with the opinion, that the seventh is 

 simply a nerve of voluntary motion. It will afterwards appear 

 that it has no claim to any further endowment. 



Mr. Herbert Mayo infers from his experiments, that the three 

 divisions of the eighth pair are all nerves both of motion and 

 sensation. Thus the glossopharyngeus is a nerve of motion to 

 the pharynx, and perhaps of sensibility to the tongue. He 

 observed that " on irritating the glossopharyngeal nerve in an 

 animal recently killed, the muscular fibres about the pharynx 

 acted, but not those of the tongue f." Irritation of the spinal 

 accessory produced both muscular contractions and pain. The 

 par vagum, he conceives, bestows sensibility on the membrane 

 of the larynx, besides conveying the motive stimulus to its 

 muscles. This nerve has been the subject of experiment from 

 the earliest times, and Legallois has minutely described the 

 results obtained by successive inquirers]:. These were singu- 

 larly discordant, and gave origin to the most opposite theories 

 of the mode of action of the par vagum. In the greater number 

 of experiments, section of this nerve was followed, after a longer 

 or shorter interval, by death. Piccolhomini contended that the 

 division of the nerve was fatal from its arresting the move- 

 ments of the heart, and after him Willis supported the same 

 doctrine. By Haller, on the contrary, the cause of death was 

 sought in disturbance of the digestive functions. Bichat and 

 Dupuytren seem to have been the first to obtain a glimpse of the 

 true seat of injury. The former remarked that the respiration 

 became very laborious after section of the nerve, and Dupuytren 

 distinctly traced death to asphyxia. Legallois has established 

 by numerous experiments the accuracy of this last view. He 

 has shown that in very young animals death is the immediate 

 consequence of the operation of cutting either the par vagum 

 or its recurrent branch, and that the suddenness of the effect 

 is due to the narrowness of the aperture of the glottis in early 

 age. In adult animals, the asphyxia is induced by the effusion 

 of serous fluids and ropy discoloured mucus into the bronchial 

 tubes and air-cells. More recently, Dr. Wilson Philip has prac- 

 tised the section of the par vagum with an especial reference 

 to its influence upon digestion. He divided the nerve below 

 the origin of the inferior laryngeal branch, as in this case the 



* pp. 106, 107. t Outlines of Human Physiology, 2nd edit., p. 337. 



X (Envres, p. 1 54 et seq. 



