

62 THE PINEAL ORGAN 



edge of the pallium in the Scallop (Pecten) (Figs. 106, 107, Chap. 12, pp. 148, 

 149). The same type of simple upright eye is also seen in the " pineal 

 eyes " of cyclostomes and reptiles, in which a clear area free from pigment 

 lies immediately over the pineal organ. Incidentally, it may be mentioned 

 that pigment is sometimes present in the part of the pineal vesicle which 

 gives rise to the lens, both in cyclostomes and in some reptiles, e.g. the 

 blind worm, Anguis fragilis. The pigment found in this situation is 

 probably a degenerative product, and indicates the vestigial nature of the 

 " pineal eye." 



Quast distinguishes two kinds of pigment in the pineal gland of man. 

 Yellow pigment, present in the cells of the parenchyma, which results 

 from the wear and tear or breaking down of the parenchyma cells — 

 " Abnutzungspigmente " ; and black pigment, or melanin, which is 

 found in the interstitial tissue. 1 The characteristic features of these are 

 contrasted in the following table : 



Yellow Pigment Black Pigment 



Parenchymal pigment. Waste Pigment of the membranes and of the 



pigment. interstitial tissue. Melanin. 



1 . Irregular masses of granules of 1 . Granules almost always of approxi- 



different size often clumped mately the same size, and of 



together. uniformly spherical form. 



2. Granules rather coarse. 2. Fine granules. 



3. Clear, glistening, yellow-brown 3. Dark brown colour. 



colour (though in aged subjects 

 it may take on a deeper tone 

 which does not differ much from 

 the pigment of the interstitial 

 tissue). 



4. Feebly stainable. 4. Relatively deeply stainable. 



5. Stains with basic dyes, especially 5. Does not stain with basic dyes, 



after the removal of fat or either before or after bleaching, 



bleaching. 



Quast describes varying degrees of pigmentation of the parenchyma 

 cells, and emphasizes the extreme fineness of the pigment granules found 

 in the interstitial tissues, more especially in some of the branched pigment 

 cells and elongated cells following the course of the larger vessels in the 

 connective tissue septa and in the connective tissue of the membranes 

 (investing layer of pia mater). Quast, referring to a case of primary 

 melanotic sarcoma in the epiphysis of a woman aged 32, states that Ogle 

 described the normal pineal gland as containing only a very small amount 



1 With reference to the use of the term " interstitial tissue " as denoting the 

 supporting tissue of the " parenchyma cells," it is necessary to state that this is a 

 complex tissue composed largely of a glial reticulum which is epithelial in origin, 

 but also containing connective tissue elements, derived from the pia mater investing 

 the pineal organ and carried into its substance by the vessels. 



