HISTOLOGY OP THE POSTERIOR PITUITARY. 495 



Again do we find the closed glands, or alveoli, including the 

 colloid substance. Again are the glandular elements supported 

 by connective-tissue trabeculaB permeated with capillaries, 

 though the caliber of the larger vessels is somewhat smaller. 

 Yet a feature which seems to us important the colloid 

 alveoli are always most numerous near the outer edge of the 

 ependymal cells, that portion farthest away from the inter- 

 lobular partition, while the space between these structures and 

 the partition is occupied by cellular elements of an entirely 

 different kind. 



The third portion may be said to occupy nearly two-thirds 

 of the entire lobe: a perfect maze of nervous elements, some 

 of which have not so far been found elsewhere in the organism. 

 Yet connective-tissue partitions carrying blood-vessels are dis- 

 cernible throughout this entire area: a feature which suggests 

 that an orderly subdivision exists. Its nervous elements vary 

 greatly in form, but they may be divided into three general 

 classes: 1. Cells that give off protoplasmic extensions, neu- 

 raxons, etc., that are not sufficiently long to reach the upper, 

 anterior region of the lobe: t.0., the infundibular region. 2. 

 Cells the extensions of which reach this region. 3. Cells that 

 are found mainly or only in this portion of the organ. 



The first class includes flask-like cells with knot-tipped 

 fibers that recall those of the anterior lobe (Fig. A, Plate I, 

 and Fig. a, Plate II). These bodies are widely distributed, 

 but their multitude of ramifications end freely among neigh- 

 boring structures. Similar, though smaller, cells (Fig. B, Plate 

 I, and Fig. &, Plate II) are found chiefly in the center, and 

 have processes that extend upward a considerable distance and 

 there often terminate in a brush-like figure. In this class may 

 be included peculiar oval bodies (Fig. (7, Plate I, and Fig. c, 

 Plate II), mainly found in the center of the organ, that recall 

 closed follicles. They give off axis-cylinders that coil about 

 them irregularly, and fibers which terminate either in irreg- 

 ular figures resembling combs with knob-tipped teeth or in 

 cat-o'-nine-tail-like tufts. Neuroglia cells, especially those of 

 the mossy kind, are shown in Fig. d, Plate II, while spider- 

 cells (Fig. E, Plate I, and Fig. e, Plate II) are mainly found 

 where the nerve-cells are very numerous: i.e., the anterior third 



