THE CRANIAL NERVES. 465 



coming from the infraorbital nerve. The upper and lower lips are both 

 supplied from the infraorbital and mental nerves on the outside, and 

 from the terminal filaments of the buccal nerve on the inside ; and the 

 temporal region receives branches both from the superior and inferior 

 maxillary divisions. A most important anastomotic branch is that to 

 the facial nerve (Fig. 123, /), which it supplies with sensitive filaments. 

 Many of these filaments no doubt terminate in the facial muscles, to 

 which they communicate a certain amount of sensibility ; but there are 

 also abundant anastomoses between the facial nerve and the fifth near 

 their final distributions, and certain regions of the integument may be 

 supplied with sensibility from this source. The observations of L'Etie- 

 vant * show that it is impossible, in man, to abolish completely the sen- 

 sibility of any extended region of the face by section of a single division 

 of the fifth pair ; some degree of sensibility still remaining, due to in- 

 osculatory filaments from other divisions of the nerve, either directly 

 or through the branches of the facial. 



According to Henle, there is still a portion of the side of the face 

 which may derive sensibility from the great auricular nerve of the 

 cervical plexus ; since the anterior branch of this nerve, after supply- 

 ing the under part of the lobe of the ear, sends some slender filaments 

 forward to the integument of the cheeks, in some instances as far as 

 the neighborhood of the malar bone. 



Influence of the Fifth Pair on the Special Senses. This nerve has 

 an important connection with the special senses, since they are more 

 or less impaired, and in some instances practically destroyed, by its 

 division or injury. Its influence, however, is mainly indirect ; showing 

 itself for the most part by disturbance of nutrition in the tissues of the 

 organ after the nerve has been cut off. These effects seem to depend, 

 not on the division of the ordinary sensitive fibres of the nerve, but on 

 that of sympathetic fibres derived from the Gasserian ganglion, or sup- 

 plied, through its branches, to the organs of sense. 



Influence on the Sense of Smell. The nasal passages are supplied 

 by two different cerebro-spinal nerves, namely, the olfactory nerve, 

 distributed to their upper portions, and endowed with special sensi- 

 bility ; and the nasal branches of the fifth pair, distributed in the lower 

 portions, to which they communicate general sensibility. The mucous 

 membrane also contains filaments from the spheno-palatine ganglion 

 of the sympathetic ; which, in turn, receives its sensitive root from the 

 superior maxillary division of the fifth pair. 



The general sensibility of the nasal passages may accordingly remain 

 after the sense of smell has been destroyed. But if the fifth pair be 

 divided, not only is general sensibility abolished in the nasal mucous 

 membrane, but there is also a disturbance in its nutrition, which 

 destroys the power of smell. The membrane becomes swollen, and 

 the passages are obstructed by accumulation of mucus. According to 



* Traite des Sections Nerveuses. Paris, 1873, p. 179. 

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