THE PIGMENT-CELLS OF THE PINEAL BODY 63 



of melanin pigment, but not so small as to exclude the growth of a primary 

 melanotic tumour. In the case described the pigment was of a brown 

 colour and distributed in the parenchyma cells of the gland. The primary 

 presence of pigment in the epiphysis, according to Ogle, is otherwise only 

 to be seen in cases of cystic degeneration. Although pigment is scanty 

 in the normal pineal body in man, it is abundant in the cells and connective 

 tissue of the pineal in the horse and ass. 



Quast concludes by stating that " the pigment cells of the interstitial 

 tissue are, on morphological grounds, to be regarded as chromatophores. 

 The chromatophores contain only one kind of pigment, melanin. The 

 pigment of the interstitial tissue of the pineal considered from every 

 aspect, namely from its morphological, physical, and optical characters, 

 including its microchemical and staining reactions, belongs to the meso- 

 dermal, melanin type." 



With reference to the parenchyma pigment he states that the older 

 the patient the greater the pigment content of the parenchyma. 



The morphological significance of the type of pigment found in the 

 pineal body of mammalia lies in the indications that it may give, first, 

 as to whether its presence may be regarded as evidence of its vestigial 

 nature, namely, whether a particular kind of pigment indicates the deriva- 

 tion of the epiphysis from the " pineal eye " of lower types of vertebrates ; 

 or, secondly, whether it throws any light on the view, maintained by some 

 authors, that the mammalian epiphysis is a newly evolved glandular 

 structure, which differs in structure and in function from the parietal 

 organ of cyclostomes, reptiles, and Amphibia. Again, whether the 

 presence of pigment in the organ is merely incidental, being derived from 

 the pia mater covering the organ, or results from degenerative processes 

 occurring in the parenchyma cells of the gland, which processes are com- 

 parable to the katabolic products of actively secreting glands. 



Like Quast, who studied the pigment of the mammalian epiphysis, 

 Ley dig, working on the " pineal eye " of reptiles and cyclostomes, dis- 

 tinguished two kinds of pigment. The one present in small amount and 

 having the dark (brown-black) type of granule, the other when seen with 

 transmitted light having the dusky-yellow granule, which corresponds 

 closely to the guanin-containing pigment of the skin. With reflected 

 light these granules in the retinal cells of the " pineal eye " of cylostomes 

 appear white. The latter type of pigment was in Leydig's opinion com- 

 parable with pigments containing uric acid. Studnicka confirmed Leydig's 

 opinion of there being two types of pigment in the "pineal eye " of 

 cyclostomes : there being a small amount of pigment consisting of fine 

 granules widely separated from one another and of a dark brown colour 

 found in the supporting tissue of the retina, this latter type being 



