PINEAL BODY 387 



connection with the connective-tissue elements. The con- 

 nective-tissue septa and bands carry in numerous bloodvessels 

 and nerves, of which some are doubly contoured. 



The cylindrical epithelium of the ependyma not only covers 

 the part of the pineal body which is nearest to the brain 

 ventricle, but lines certain hollow spaces found within the body 

 of the gland itself. The majority of these hollow cavities 

 become obliterated by the proliferation of their lining cells. 



There appear to be no true nerve cells in the adult mammalian 

 body. It is stated that there are nerve fibres derived from the 

 brain substance as well as sympa- 

 thetic fibres, which enter, along with 

 the bloodvessels, in the interior of the 

 pineal body. 



The parenchyma of the gland is 

 made up of follicles, which, however, Ji ;.' 

 are only sharply marked out at the ^ 

 periphery of the organ (Fig. 104). The 

 cells of these follicles have sometimes 

 been described as resembling those of 

 adenoid tissue. 



An exact description of the con- 

 stituent cells of the follicles cannot be v ' ' 

 compiled from the accounts of the 

 various writers upon the subject. It 



seems clear, however, that the cells FIQ w ^ eci ^ n ^ the 

 are of two chief kinds neuroglia and pineal gland of the sheep, 

 secretory cells. The latter are slightly ^J b y Mrs - Thom P- 

 stainable with a large oval granular 



nucleus. The cell body contains granules, either distributed 

 throughout its substance, or arranged round the periphery. 

 Galeotti described secretory processes in these cells. 



The "brain-sand" ("acervulus cerebri") which occurs in 

 certain follicles, has been known from the earliest times. It 

 has not been shown to be of any physiological importance. 

 It is found also in the choroid plexus and in the pia mater of 

 the lobus olfactorius. 



Cysts are also found in the pineal body. 



Cutore has recently described a structure in the pineal body 

 of the ox which is of doubtful significance. It is a rounded 

 body of variable size in the roof of the diencephalon. It may 



