THE PINEAL ORGAN OF MAMMALS 



325 



activity of the cell-elements might be stimulated by the action of hormones 

 circulating in the blood, or by efferent inpulses reaching the organ by 

 means of sympathetic nerve-fibres terminating in direct relation with the 



ch ,PO 



co. i 

 olH mint 



Fig. 225. — Median Vertical Section through Brain of a Rabbit, Lepus 

 cuniculus, showing plneal organ with long narrow stalk, situated 

 behind the splenium of the corpus callosum. (after parker.) 



ca. : anterior commissure. 

 Mm. : cerebellum. 

 c.c. : Corpus callosum. 

 ch. : habenular commissure. 



cp. : posterior commissure. 

 m. int. : massa intermedia. 

 olf. I. : olfactory lobe. 

 p.o. : pineal organ. 



parenchyma cells. The epiphysis in these rodents is, however, small 

 and imperfectly developed with respect to its microscopical structure ; 

 and it appears to be very doubtful whether true secretory nerve-fibres 

 are actually present in direct association with the cell-elements. The 



, hob ,, „ R.V.111 

 ^Hip.Com/ 



,M.lnb. 

 V X^<>/C.PT. 



W$$&fewm. >S> C - c c . 



Fig. 226. 



-Median Sagittal Section 

 (After 



A.C. : anterior commissure. 



C.C. : corpus callosum. 



Ch. : optic chiasma. 



CM. : corpus mammillare. 



C. Op. : colliculus opticus. 



C.P. : posterior commissure. 



C.P.T. : corpus paraterminalis. 



F.M. : foramen of Monro. 



G. IP. : ganglion interpedunculare. 



"Pit 



THROUGH THE PlNEAL REGION OF A SHEEP. 

 J. WlLKIE.) 



Hab. : habenular ganglion. 



Hip. Com. : hippocampal commissure. 



Inf. : infundibulum. 



L.T. : lamina terminalis. 



M. Int. : massa intermedia. 



P. : pons. 



Pin. : pineal 



R.V. III. : roof of third ventricle. 



5. Pin. R. : suprapineal recess. 



condition of the separated end-organ of the adult rat is very similar to 

 that of Stieda's organ of the frog, namely, a degenerate vestige, which 

 has lost the characteristic features of the parietal eye, and does not show 



