168 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Pineal Body of Sheep* — H. E. Jordan finds that this body begins 

 as usual as an evagination from the roof of the diencephalon. At the 

 2 • 5 cm. stage it has the form of a definite pocket lined with ependyma 

 thickened distally. 



At the 5 cm. stage the cells of the distal and dorsal walls have become 

 stellate, with anastomosing processes forming a loose-meshed syncytial 

 network. This represents the first stage in the formation of the neuroglia 

 framework. A few of the cells contain some melanoid (melanic) granules. 



The body takes a backward direction in growth ; the apical cells pro- 

 liferate more actively, thus forming a rounded dome-shaped body with a 

 shallow proximal pineal recess continuous with the third ventricle. Blind 

 alveoli (cysts) make their appearance, and the pia mater sends in 

 vascular trabecule, dividing the body into lobules. 



The same processes continue to half term (21 cm.), when proliferation 

 seems most active. The pigment-granules are now most abundant, the 

 " alveoli " largest and most numerous. At birth the pineal body is Id a 

 similar condition, but larger. There are, besides, follicular collections of 

 cells with central vascular trabecula or capillary network, surrounded by 

 a wide peri-vascular lymph-space. 



Between birth and the end of the first year the pineal body enlarges, 

 approximately, five-fold. The pigment-granules have been distributed ; 

 vascular follicles are abundant ; an occasional cyst remains ; medullated 

 nerve-fibres can be traced into the basal portion and in relation to the 

 blood-vessels ; the parenchyma consists of one type — a more or less dif- 

 ferentiated ependymal cell. 



After the first year signs of local degeneration appear, i.e. increase of 

 connective-tissue and neuroglia, and the appearance of brain-sand, 

 large clumps of pigment-granules, cell-free areas of oedematous neu- 

 roglia network, and a decrease of parenchyma cells. 



There is no clear histological evidence indicative of a glandular 

 function. If the pineal body of the sheep subserves an important 

 function, this is probably restricted to the first eight months of post- 

 natal life. The only cytoplasmic granules are melanic, and probably 

 have only ancestral significance. The cysts are similarly interpreted. 

 The neuroglia fibres appear to have their origin in the thickened and 

 fused spongioplasmic fibres. 



Melanotic Pigment in the Embryonic Eye and in Malignant 

 Tumours.j — Aurel v. Szilly finds that in both these cases the black 

 pigment has its basis in colourless stromata, the so-called pigment- 

 bearers. These bodies are specific in different animals and in different 

 situations. They arise from the chromatin of the nucleus, and pass into 

 the cytoplasm. They are comparable to chromidia. Some are active or 

 productive, appearing without injury to the efficiency of the nucleus. 

 This is the case in the origin of the colourless pigment-bearers in the 

 retina of the chick-embryo. Others are of a degenerative type, and their 

 appearance is associated with a partial or total breakdown of the nucleus, 

 as in the pigment epithelium of the eye in mammalian embryos, or 

 in the pigmentation of melanotic sarcoma. The change of colourless 



♦ Amer. Journ. Anat., xii. (1911) pp. 249-70 (3 pis.)- 

 t Arch. Mikr. Anat., Ixxvii. (1911) pp. 87-156 (4 pis.). 



