THE PINEAL BODY OF THE SHEEP 261 



REVIEW OF LITERATURE 



Only Flesch ('88) and Dimitrova ('01) in their comparative 

 studies of the pineal body of various mammals have p§id special 

 attention to that of sheep. But Flesch studied more particularly 

 the epiphysis of the dog and the bat, and Dimitrova reports more 

 fully on appearances in ox, calf, cat, and man, observing that the 

 body of the sheep is very similar to that of the ox. This general 

 neglect to make a careful and detailed study of the pineal body of 

 the sheep is the more remarkable when one recalls its large size 

 and its easy availability. 



Flesch argues for the non-rudimentary condition and for an 

 important physiologic significance of the adult pineal body in 

 man and mammals on the basis: (1) its nerve supply (from 

 optic thalamus ; Kolliker, '96) ; (2) peculiar general characteris- 

 tics (lobulation; pigmentation); and (3) presence of specific 

 cells. To these might well have been added a fourth point; viz., 

 its great vascularity. Flesch notes lymph cells in process of 

 transit from the pineal recess through the lining ependyraa, and 

 their presence in the coagulated content of the recess; neither of 

 which observations I can confirm. Flesch summarizes the main 

 evidence in support of the secretory significance as (1) the large 

 amount of coagulum in the recessus pinealis, and (2) the presence 

 of pigment granules in the specific cells; and in opposition thereto 

 as (1) absence of a specific reaction of the parenchyma which 

 would indicate a specific chemical activity, (2) no correspondence 

 between size of gland and central nervous system nor to size of 

 body as a whole. He notes that in spite of small size of sheep's 

 brain the pineal body is relatively large. It is about half as large 

 as in man, according to Flesch, but of about the same size accord- 

 ing, to my observations. In view of the above considerations, 

 more particularly on the basis of the presence of pigment, Flesch 

 is inclined to regard the pineal body of mammals as a modified 

 sense-organ which has lost its primitive visual function. Regard- 

 ing the question of a possible secondary function, we stand here 

 before a riddle which can only be solved by experimental methods 

 of investigation. 



