196 CLINICAL APPLIED ANATOMY. 



be damaged by growths of the adjacent pituitary body, by 

 aneurysm of the internal carotid artery, by periostitis at the 

 sphenoidal fissure, or by lesions in the orbit. The close relation 

 of this nerve to the cavernous sinus constitutes a serious diffi- 

 culty in the complete removal of the Gasserian ganglion. 



The maxillary division, after its exit from the skull by the 

 foramen rotundum, traverses the spheno-maxillary fossa, applies 

 itself closely to the orbital aspect of the palate bone, and enters 

 the infraorbital canal. It may be damaged by bone disease or 

 fractures. Its relation to the maxillary antrum, in the roof of 

 which it lies, accounts for the paralysis caused by maxillary 

 tumours and the neuralgia which may result from antral disease. 



The mandibular nerve, unlike the other two divisions, con- 

 tains motor as well as sensory fibres. This division is rarely 

 the sole seat of paralysis, but is sometimes damaged by fractures 

 or callus of the mandible and by parotid tumours. 



The motor filaments of the fifth supply the muscles of 

 mastication. Of these the temporals and masseters are super- 

 ficial, and their action can be gauged by feeling the hardening 

 they undergo when called into action. Wasting of these 

 muscles causes flattening above and below the zygoma, and 

 if they undergo secondary contracture they may interfere with 

 the free opening of the mouth. Loss of power in the pterygoid 

 muscles causes the lower jaw to deviate towards the paralysed 

 side when the mouth is opened, owing to the unbalanced action 

 of the muscles of the opposite side. The tensor palati which 

 appears to derive its motor nerve from the fifth, is probably 

 innervated from the spinal accessory nucleus, and escapes in 

 ordinary fifth nerve paralysis. Paralysis of the mylo-hyoid and 

 anterior belly of the digastric, both of which are supplied by 

 the mylo-hyoid branch of the inferior dental nerve, is not easily 

 recognised clinically, other muscles being also able to elevate 

 the hyoid bone. Earely irritation of a sensory filament of the 

 fifth causes trismus or tonic contraction of the muscles of 

 mastication. This is said to be especially associated with irrita- 

 tion of the last molar tooth from caries or abscess. It may also 



