THE PINEAL BODY 177 



The pineal body is cylindricoeonical in form in Macacus sinicus 

 and presents a great number of nerve fibers. 



3. Cercopithecus griseus viridis. Cutore ('10). 76 In this 

 species the dimensions of the pineal body are: 



cm. 



Longitudinal 0.3 



Transverse 0.2 



Anteroposterior 0.2 



The pineal body in this form is conical in shape. The struc- 

 ture of the organ is evidently glandular. 



4. Homo sapiens. A large number of observers have given 

 their attention to the pineal body in man and many diverse 

 opinions have been expressed concerning it. Cutore's 76 sum- 

 mary giving the histology and dimensions of the pineal body in 

 man is the most recent and complete review. The figures have 

 already been cited (p. 157). Cutore concludes that the human 

 pineal body develops slowly, retaining even up to the time of 

 birth its primitive diverticular form. In the adult, however, 

 this organ has become relatively voluminous and the original 

 recess is much reduced to form the ventriculus or recessus 

 pinealis. The superior or habenular commissure is small. The 

 pineal fibers are limited in number and distributed to the inferior 

 third of the organ. In the disposition of the parenchyma there 

 is seen a distinct tendency for the cells to arrange themselves 

 in circular areas clearly delimiting small cavities in which there 

 appears an amorphous or crystalline substance. Elastic tissue 

 is scanty, but pigment cells are numerous and concretions of 

 varying sizes appear in large numbers. The vascularization is 

 rich especially around the aciniform groups of cells. Neuroglia 

 and cylindrical ependymal cells are also present. Connective- 

 tissue processes from the pia mater form an irregular partition 

 of the tissue into lobules. Siegneur 351 considers the pineal body 

 in man a gland, the cells of which are of two types, those which 

 are polyhedral with granules in the cytoplasm. These granules 

 are most numerous about the nucleus. Some of the cells have 

 vacuoles. The second type of cells are even larger and contain 

 large nuclei which stain deeply and occupy an excentric position in 



MEMOIR NO. 9 



