THE PINEAL BODY 213 



tion. In ophidians and chelonians the parapineal organ is 

 entirely absent, and the only element of the pineal organ which 

 persists is the proximal portion which has become converted into 

 a more or less solid structure extending from the roof of the brain 

 dorsad toward the vault of the skull. Similarly, in birds and 

 mammals, the only element of the epiphyseal complex which 

 may be recognized is the proximal portion of the pineal organ. 

 This, as in reptiles, is an organ of considerable density close to 

 the roof of the brain. 



From these facts it will be seen that the proximal portion of 

 the pineal organ is the most constant element of the epiphyseal 

 complex, the next in point of frequency being the end-vesicle 

 and stalk of the pineal organ. It would seem, therefore, that the 

 proximal portion of the pineal organ should be considered the 

 fundamental element of the epiphyseal complex, and its struc- 

 ture would, therefore, demand particular attention. That this 

 element in the epiphyseal complex does show a marked tendency 

 toward specialization from the selachians to reptiles, birds and 

 mammals is convincing evidence that this structure is not to be 

 considered a vestige, for were such the case it would scarcely 

 manifest such a definite tendency toward specialization in the 

 processes of evolution. 



e. The epiphy so-cerebral index. Not alone is the evidence 

 obtained from the comparative studies of the pineal body in 

 favor of its progressive specialization, but quite as much the 

 facts obtained from ontogenesis of the organ in man. We are 

 fortunate to possesss a careful series of observations made by 

 Cut ore 76 in which the weight of the brain as well as the weight 

 of the epiphysis and the hypophysis have been recorded. These 

 statistics are based upon the observations ranging from the new- 

 born to the seventieth year of life. In all, twenty-five brains 

 were studied, and it would seem that from such material, limited 

 though it may be, some light might be shed upon the ontogenetic 

 evolution, upon the epiphysis in its relation to the rest of the 

 brain and also to a recognized endocrinal organ, the hypophysis, 



If, as has been frequently maintained, the pineal body is a 

 vestige and of no functional significance, then the tendency for 



