CHAPTER 33 



GENERAL CONCLUSIONS 



The surgery of the pineal organ, although yet in its infancy, may be said 

 to be advancing rapidly owing to the fact that neurological diagnosis 

 becomes more established and more accurate each year. 



The symptomatology tends to be more definite : there is usually a 

 severe degree of raised intracranial pressure, associated with headache, 

 vomiting, papilledema, epileptiform fits, and some cranial nerve paralysis. 

 The eye signs are definite, with loss of pupillary reaction and failure of 

 upward movement of the eyes. 



Operations for the removal of pineal tumours have become standard- 

 ized ; and even if the complete removal cannot be undertaken, a post- 

 operative course of deep X-ray therapy will complete the cure, as the 

 majority of pineal tumours are radio-sensitive. 



Morphology 



1. The pineal system, including the parietal eye, its nerves, and the 

 related cerebral ganglia is one of the most ancient sensory systems of 

 the vertebrate phylum. The existence of a parietal sense-organ being 

 plainly indicated in certain of the primitive ostracoderm fishes by the 

 presence of a pineal plate, showing either a complete pineal canal or a 

 pineal pit on the inner surface of the plate. The canal and plate are well 

 seen in the examples of Anaspida and Cephalaspida, which are found in 

 strata ranging from the lower Silurian 1 to the Devonian eras and in speci- 

 mens of Pterichthys and Bothriolepis belonging to the Order Antiarchi, 

 found in upper Devonian strata. 



2. In these fishes there is definite evidence that the parietal eye 

 coexisted with other sensory organs of the head, namely : the lateral 

 eyes, the olfactory organs, and the vestibular or static organs ; and also 

 that these had approximately the same relative positions to each other 

 and the parietal foramen or pit that they have in the heads of living 

 cyclostomes and other vertebrates. 



3. The closure of the outer or superficial end of the parietal canal by 

 a thin plate of bone in certain examples indicates that in these specimens 



1 The Silurian Epoch has been estimated by Barrell to embrace a period from 

 390,000,000 to 460,000,000 years ago. 



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