THE PINEAL BODY OF THE SHEEP 265 



light perceptive organ, the production of pigment in the homol- 

 ogous cells of this mammalian pineal vestige becomes intelligible 

 in terms of an hereditary attempt to subserve phylogenetically 

 earlier functions. The nature of the stimulus that incites to such 

 great post-natal proliferative activity in some forms is the riddle 

 that baffles speculation.^ As above stated, there is discernible 

 no further evidence for a secretory function. The vacuoles noted 

 by Dimitrova — present also in the cells of the sheep's pineal body 

 — do not seem to me to have the value of vesicles of a specific secre- 

 tion (colloid?) as suggested by Dimitrova. The smaller and more 

 nearly spherical cells have a homogeneous cytoplasm. The larger 

 and more irregular cells are the more vacuolated and reticular. 

 The vacuolization appears to be due to a mechanical adjustment 

 of the cytoplasm to enlarging confines; a sign of age (or differ- 

 entiation) or degeneration. 



^A subsequent search for possible secietory granules in pineal bodies of young 

 sheep, by means of the Altmann technic, has revealed a granular character of the 

 cytoplasm in material so treated. Samples from the same pineal body fixed in a 10 

 per cent formaldehyde solution show the usual very finely granular or homogeneous 

 structure of the cytoplasm of the parenchymal cells. The more coarsely granular 

 character of the cytoplasm thus seems due to the action of the modified Flemming's 

 fluid (equal parts of a 2 per cent solution of osmic acid and a 5 per cent aqueous 

 solution of potassium dichromate), and is more probably of the nature of an arti- 

 fact. The Altmann technic, however, reveals the presence of certain lipoid bodies 

 which were lost by all the other methods of preservation employed. In samples of 

 the same body (perfectly fresh), fixed in formaldehyde, these were missing. They 

 were lost also in material which was differentiated in the picro-alcohol solution 

 for more than a fraction of a minute or passed too slowly through the alcohol in 

 dehydrating for mounting. These bodies, accordingly, are highly soluble lipoids, 

 which disappear in all ordinary technics where alcohol is used. The occasional 

 presence of a few light brown or yellowish melanic granules, contrasting sharply 

 with the dark brown and black color of the lipoid granules, leaves no ground for 

 possible confusion. The granules in question are larger and smaller spheres, the 

 majority of which seem to be disintegrating giving rise to spherical masses of very 

 small black granules. The original 'sphere' is represented by a lighter substance in 

 which the smaller granules are embedded. Some spheres contain only a few 

 granules. The solid lipoid sphere seems to pass through this as an intermediate 

 stage to one of more fluid form. 



The vacuoles seen in the cytoplasm of the parench>Tnal cells of the same tissue 

 treated with the formalin technic undoubtedly represent the lipoid bodies after 

 solution, and this is probably the origin also of at least some of the vacuoles occa- 

 sionally seen after treatment with the usual technics involving the relatively pro- 

 longed use of alcohol. These occasional lipoid bodies probably indicate intra- 

 cellular degenerative changes, and are not mitochondrial nor secretory in nature. 



THE AMERICAN JOURNAL OF ANATOMY, VOL,. 12, NO. 3 



