SYMPTOMATOLOGY OF PINEAL TUMOURS 437 



development. It is extremely common to find that the light reflex is absent 

 and the patient unable to look upward. 



To understand this clearly it is necessary to visualize the arrangement 

 of the oculomotor nuclei (Fig. 288). It will be remembered that the 

 nuclei of the Illrd, IVth, and Vlth nerves lie in about one continuous 

 line on either side of the aqueduct just below the corpora quadrigemina, 

 together with the medially placed nuclei. Various functions have been 

 mapped out for the several parts of the nucleus. In Fig. 288 it will be 

 seen that the Edinger-Westphal nucleus (A) is the most anterior, and is 

 concerned with control of the pupillary and ciliary muscles ; the dorsi- 



/-- Bird Ventricle 



A 



^v Central 



|V\ ..--Nucleus 



- B 



- C 



Fig. 288. — Diagram showing Arrangement of Oculomotor Nuclei. 



lateral nucleus (B) is concerned with upward movements ; the ventro- 

 medial nucleus (C) is concerned with downward movement ; the central 

 nucleus with movements of divergence. The small caudal nucleus (D) 

 may be concerned again with pupillary reaction. 



Thus it will be seen that pressure exerted from in front and above 

 the nuclei will give rise first to absence of light reflex, then to loss of 

 accommodation and loss of upward and downward movement. In clinical 

 practice it is the lateral movements which persist for the longest period. 



Ear Signs. — Should the inferior corpora quadrigemina be pressed 

 upon, then deafness, unilateral or bilateral, complete or partial, may result. 



