6 FREDERICK TILNEY AND LUTHER F. WARREN 



would seem ill-advised. The separation between those who 

 consider the pineal body a useless vestige and those who assign 

 to it extensive responsibilities in the sphere of internal secretion 

 is too great to be reconciled on any but the most careful investi- 

 gation of the grounds for their differences. The phylogenesis of 

 the organ among the vertebrates, especially in its relation to 

 the third or parietal eye, as well as the significance of the struc- 

 ture as a possible mark of identification in the line of evolution 

 from the invertebrate to the vertebrate phylum, has raised many 

 perplexing questions. Although the researches of morphologists, 

 physiologists, and clinicians have established many significant 

 facts, it still remains to assemble this evidence as much in its 

 entirety as possible in order to furnish a satisfactory basis for 

 the discussion of the problem. 



It is the purpose of this work to gather the recorded facts 

 concerning the pineal body and present them in several parts 

 under the following headings : 



Part I. The morphology and evolutional significance of the 

 pineal body. 



Part II. The physiology and pathology of the pineal body. 



Part III. The clinical aspects of the pineal body. 



