256 H. E. JORDAN 



loops or 'glomeruli' within spaces surrounded by more compact 

 parenchyma. Such spaces in some cases represent alveoli into 

 which a trabecula has carried blood-vessels (fig. 5). It remains to 

 note that both the parenchyma and neuroglia fibers are more 

 abundant peripherally. The latter also are coarser in this region. 

 The entire body, exclusive of the vascular pial trabeculae and a 

 few white nerve fibers, is composed of more highly differentiated 

 or neuroglia cells with fibers, and less highly differentiated or 

 inter-neuroglia cells of the original ependymaof the third ventricle. 



THE PINEAL BODY OF LAMBS 



In young sheep (ca. 8 months) the pineal body attains the greatest 

 size (ca. 8 mm. x 5 mm.). Its structure is identical with that 

 of bodies at birth ; the only difference being one of greater mass of 

 the same constituent elements in the latter (fig. 8). The cell 

 increase has been at least predominantly by mitosis. Occasion- 

 ally cells are binucleate, the result apparently of amitotic 

 nuclear division, indicating the probability of a second contrib- 

 utory method of multiplication. Compared with the epiphysis 

 of embryos, the nuclei of the constituent cells in young sheep 

 are considerably larger (compare figs. 3 and 8). In the latter, 

 the nucleus measures approximately eight microns and the 

 cell body of the spherical and polygonal type approximately 15 

 microns. Increase in total size of the pineal body then may be 

 due in part also to the enlargement of individual cells. The 

 greatest increase in bulk (approximately five-fold) during the first 

 year indicates that if the pineal body has a specific function this 

 is most active in the young; and the suggestion frequently made 

 that the body is a gland which elaborates an internal secretion 

 which has to do with the normal growth or the appearance of 

 sexual maturity (sheep mate at from 6 to 8 months) receives sup- 

 port from anatomical facts. 



Observations on human corpora pinealia in my collection point 

 to the same conclusion. In an infant of five days the body has 

 the shape and about the size of a small grain of wheat. It is 

 sharply pointed distally and flattened dorso-ventrally. Its dimen- 

 sions are approximately 3 mm. x 2 mm. x 1 mm. In infants of 



