634 NERVOUS SYSTEM. 



The sublingual may be easily exposed in the dog by making an incision just below 

 the border of the lower jaw, dissecting down to the carotid artery and following the 

 vessel upward until we see the nerve as it crosses its course. On applying a feeble 

 current of galvanism at this point, there are evidences of sensibility, and the tongue is 

 moved convulsively at each stimulation. 



The phenomena following section of both sublingual nerves point directly to their 

 function. The most notable fact observed after this operation is, that the movements of 

 the tongue are entirely lost, while general sensibility and the sense of taste are not affected, j 

 The phenomena which follow division of these nerves consist simply in loss of power 

 over the tongue, with considerable difficulty in deglutition. We have repeatedly noted 

 all of these points and have demonstrated them to medical classes. 



In the human subject, the sublingual is usually more or less affected in hemiplegia. 

 In these cases, as the patient protrudes the tongue the point is .deviated. This is due to 

 the unopposed action of the genio-hyo-glossus upon the sound side, which, as it pro- 

 trudes the tongue, directs the point toward the side affected with paralysis. 



A disease of rather rare occurrence has lately been described under the name of 

 glosso-labial paralysis, which is characterized by paralysis of the sublinguals, affecting 

 also the orbicularis oris and frequently the intrinsic muscles of the larynx. The phe- 

 nomena referable to the loss of power over the tongue correspond to those observed in 

 animals after section of the sublingual nerves. Patients affected in this way experience 

 difficulty in deglutition, and, in addition, we note an interference with articulation, which 

 cannot be observed in experiments upon animals. We lately had a case of this disease 

 under observation in the Bellevue Hospital, the phenomena of which were peculiarly 

 interesting from a physiological point of view. This patient presented complete paraly- 

 sis of the tongue, with considerable difficulty in deglutition, probably from the tongue- 

 affection. The orbicularis oris was also paralyzed. The paralysis probably extended 

 to the intrinsic muscles of the larynx, as little or no vocal sound could be made. The 

 patient was incapable of articulate language and communicated entirely by signs. 



CHAPTER XIX. 



SENSORY CRANIAL NERVES. 



Trifacial, ortrigeminal nerve Physiological anatomy of the trifacial Properties and functions of the trifacial Divi- 

 sion of the trifacial within the cranal cavity Immediate effects of division of the trifacial Remote effects of 

 division of the trifacial -Division of the trifacial before and behind the ganglion of Gasser Communication with 

 the sympathetic at the canglion of Gasser Explanation of the phenomena of disordered nutrition after division 

 of the trifacial Cases of paralysis of the trifacial in the human subject Pneumogas trie nerve (second division of 

 the eighth) Physiological anatomy Properties and functions of the pneumogastric General properties of the 

 roots Properties and functions of the auricular nerves Properties and functions of the pharyngeal nerves 

 Properties and functions of the superior laryngeal nerves Properties and functions of the inferior, or recurrent 

 laryngeal nerves Properties and functions of the cardiac nerves, and influence of the pneumogastrics upon the 

 circulation Depressor-nerve of the circulation Properties and functions of the pulmonary branches, and influ- 

 ence of the pneumogastrics upon respiration Properties and functions of the oesophageal nerves Properties and 

 functions of the abdominal branches. 



Trifacial, or Trigeminal Nerve. (Large Root of the Fifth Nerve.) 



A SINGLE nerve, the large root of the fifth pair, called the trifacial or the trigeminal, 

 gives general sensibility to the face and to the head as far back as the vertex. This is one 

 of the most interesting of the cranial nerves and is one of the first that was experimented 

 upon by physiologists. It is interesting, not only as the great sensitive nerve of the face, 

 but from its connections with other nerves and its relations to the organs of special sense. 

 In studying the physiology of this nerve, we must necessarily begin with its physiological 

 anatomy. 



