THE PARENCHYMA CELLS 399 



bring out particular characters, such as cytoplasmic granules, vacuoles, 

 lipoid material, and other contents ; also mitochondria, blepharoplasts, 

 the centrosome, and Golgi apparatus. Thus by staining frozen sections 

 with Janus green, small rod-like mitochondria may be demonstrated in 

 the pineal organ of such animals as the horse, ox, and sheep. The rods 

 are most abundant around the centrosome and the part of the cell body 

 which relative to the nucleus is the widest. Occasionally long rods or 

 chondriocontes have been observed, and one or more thick rods close 

 to the nucleus arranged in the form of crosses or bundles. Hortega 

 states that in children the rods are short, while in adults and old subjects 

 they have become elongated, their elongation coinciding with involutive 

 changes. 



The cytoplasm normally has a reticular structure, and frequently 

 shows vacuoles which may be demonstrated by the use of neutral red. 

 Lipoid material is also sometimes present. Granules of varying type are 

 normally present. Some of these have been described as secretory 

 (Dimitrowa, Rio-Hortega, Pastori, and others). There are also spherules 

 which have been thought to correspond to the " gliosomes " found in the 

 central nervous system. Some granules are apparently the result of 

 degenerative changes and are seen abundantly in the pineal cells of aged 

 subjects. Pigment granules, usually of small size, but sometimes large, 

 are found in old subjects, and like the non-pigmented granules mentioned 

 above are in some specimens due to involutive changes. These granules 

 are of a yellow-brown colour, and differ considerably from the dark 

 melanin granules which are also sometimes found in the pineal organ 

 and may be of morphological interest (see pp. 61-63). These are chiefly 

 found in the connective tissue elements, trabecular, capsule, and the 

 surrounding pial tissue. 



The nucleus of the parenchyma cells of adult subjects is typically 

 spherical, of large size, and owing to its small chromatin content appears 

 clear. A well-defined nucleolus is usually present and the nuclear mem- 

 brane is conspicuous. The nucleus of the parenchyma cells is large, 

 even in those in which the cytoplasm is scanty and the cell as a whole is 

 small as compared with the average size of these cells ; and it is also 

 large when compared with the small deeply stained nuclei of the fibroglial 

 tissue. Under certain conditions spherular formations described by 

 Dimitrowa as secretory in nature are present within the nucleus (Fig. 219, 

 Chap. 22, p. 317). These spherules have been found in the human sub- 

 ject, the ox, lamb, and other animals. They appear as clear droplets 

 which are stained red by Van Gieson's methods, a grey colour in Weigert 

 preparations, and pink with saffranin. Dimitrowa regarded the existence 

 and appearance of these spherules as undoubted evidence of secretory 



