THE MORPHOLOGY AND EVOLUTIONAL SIGNIFICANCE 

 OF THE PINEAL BODY 



The morphological problem of the epiphysis may be for.- 

 mulated in the following questions: 



1. What is the significance of the pineal region in its relation 

 to the epiphysis? 



2. Is the pineal body a vestige or is it an organ in some way 

 necessary to metabolism? 



3. Does its structure furnish evidence of its function? 



4. What relation does it bear to the third or parietal eye? 



5. What is the phylogenetic significance of the parietal eye 

 with reference to the vertebrates and invertebrates? 



Before submitting these questions to discussion, it seems 

 advisable to offer the evidence as much in extenso as is practi- 

 cable, having particular regard for historical sequence. 



2. NOMENCLATURE 



The pineal body was known to the Greeks and called by 

 them the <ro^a /aowtSes and KWVO.PLOV because of its conical 

 shape. It was also termed the epiphysis because of its relation 

 to the rest of the brain. Latin authors refer to it as the turbo, 

 corpus turbinatum, glandula turbinata, glandula piniformis, glan- 

 dula conoides, conarium, penis cerebri, and virga cerebri. 



Because of its resemblance to a pine cone, it was called by 

 Chaussier 63 and Willis 429 the corpus pineale. It has been called 

 by the Germans the Zirbel and Zirbeldruse, a designation which 

 doubtless has led to the more or less general use at present of 

 the term pineal gland. Several of the early writers called it the 

 glandula superior in contradistinction to the pituitary gland 

 which was referred to as the glandula inferior. 



Since all of these terms were, in the main, devised to meet the 

 conditions in man and the higher mammals, it might be expected 



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