THE OCULOMOTOR NERVE. 



1227 



fibres end within the latter nucleus around the cells from which the decussating fibres 

 proceed, or are actually prolonged as certain of the decussating fibres is uncertain ; 

 their purpose is to bring into coordinated action the internal rectus of one side with 

 the opposite external rectus when the two eyes are directed laterally, as in conjugate 

 deviation. 



Cortical and Central Connections. — As in the case of all other motor cranial nerves, 

 the nucleus of the third nerve stands in direct relation to the cerebral cortex. Fibres 

 from the cells of the cortical centre — axones from the neurones within the posterior part 



Olfactory bulbs 



Olfactory tract 

 Optic nerve 



Optic chiasm 



Optic tract 



III. nerve 



VII. nerve 



VIII. nen.'e 



IX. ner\-e 



X.' nerve 



XI. nerve 



XI. nerve 

 spinal portion 



Part of 

 XII. nerve 



Superior 



medullary 



velum 



Fig. 1052. 



Branch of supraorbital nerve 



Supratrochlear branch of frontal 

 Supraorbital branch of frontal 

 Lachrymal gland 



Lachrymal nerve 



Ophthalmic division of 

 V. nerve — its division 

 into frontal, lachrymai 



III. nerve [ and nasal 



Maxillary division 

 of V. nerve 



IV. nerve, to inner side 

 of which is VI. nerve 

 Mandibular division of 



V. nerve 



Gasserian ganglion 



Sensory root of V. 



VII. nerve [nerve 



VIII. nerve 

 Middle cerebellar 

 peduncle 



IX. nerve 



X. nerve, 



xn. nerve 



IV, ventricle 



Medulla, closed part 



Base of skull, viewed from above, showing cranial nerves passing through dura; roof of right orbit has been removed 



to expose the ophthalmic nerve. 



of the inferior frontal convolution, slightly in front of the precentral fissure (Mills) — proceed 

 by way of the corona radiata, the internal capsule and the cerebral peduncle to the oculo- 

 motor nucleus, around whose cells, chiefly but not exclusively on the opposite side, they 

 eud. Other connections of the nucleus of the third nerve include : (i) indirectly with the cor- 

 tical visual area by fibres that pass from the occipital cortex through the optic radiation and 

 superior brachium to the superior corpora quadrigemina ; (2) indirectly with the visual centres 

 by fibres that descend from the cells within the superior corpora quadrigemina ; (3) by means 

 of the posterior longitudinal bundle with the nuclei of the other ocular nerves (the fourth and 

 the sixth) and also with the vestibular (Deiters') nucleus of the eighth; (4) with the facial 

 nucleus by fibres that descend from the oculomotor nucleus along the posterior longitudinal 

 bundle to the cells from which proceed the fibres supplying the orbicularis palpebrarum and the 

 corrugator supercilii muscles, which are thus brought into coordinated action with the levator 

 palpebrarum. 



