476 THE PINEAL ORGAN 



neuroglial cells (astrocytes). The surrounding connective tissue and 

 ingrowing vascular mesenchyme form the fibrous capsule and the con- 

 nective tissue basis of the septa and finer trabecular, including the con- 

 tained vessels. Many of the sinusoidal vessels in the central part of the 

 pale vascular areas, which are seen in the earlier stages of development, 

 disappear, leaving only a very fine capillary plexus in the parenchymatous 

 tissue of the lobules. 



12. The parenchymatous tissue in the adult consists of a reticulum 

 of branched pineal cells, among which are a few neuroglial cells, chiefly 

 of the astrocyte type. The " alveolar " appearance which is sometimes 

 seen in adult specimens is due to the persistence of primary neuro- 

 epithelial cords, cross-sections of which appear as rosettes. 



13. Cells and nerve-fibres belonging to the sympathetic system accom- 

 pany the vessels entering and leaving the pineal organ ; and medullated 

 nerve-fibres connect the habenular and posterior commissures with the 

 parenchymatous tissue, but the exact mode of termination of their axons 

 with regard to the pineal cells is not certain. True ganglion cells belonging 

 to the central nervous system and having an axis cylinder process, although 

 described by some authors, appear to be very rarely seen in the human 

 pineal gland, but transitional forms exist, which are intermediate between 

 true nerve ceils and parenchymatous cells. These are described as 

 " neuronoid." 



The experimental and clinical evidence with respect to function of 

 the mammalian pineal body is at the present time too conflicting to allow 

 of any definite conclusions being drawn. We know that before the age 

 of puberty, more especially in boys, pineal tumours have sometimes 

 been associated with premature growth in size of the body, precocious 

 development of the genital organs, and the early appearance of secondary 

 sexual characters. But it seems probable that certain other factors have 

 been involved in the production of these symptoms — more particularly 

 pressure, either direct or indirect, of the pineal tumour on neigh- 

 bouring parts of the brain, such as the hypothalamus and pituitary 

 region, combined with the irritative reflex effects produced by in- 

 creased intracranial tension — and that the symptoms are not directly 

 attributable to disturbance of any special function possessed by the 

 pineal body itself. Moreover, a considerable number of cases have 

 been reported in which sexual precocity and macrogenitosomia have 

 been present but there has been no pineal tumour, and the reverse 

 condition in which a pineal tumour has been present in young 

 boys but unaccompanied by the Pellizzi syndrome. Further, that 

 although some cases of premature development of the breasts in 

 girls and gynecomastia in males have been reported, these con- 



