756 
MR. A. SANDERS ON THE ANATOMY OF THE 
of the epithelium lining the central canal of the spinal cord. They are surrounded by 
a layer of small circular or pear-shaped cells (fig. 21, b.), which extend for some distance 
into the substance of the hypoaria ; these cells abound more especially along the ven- 
tricles themselves, close to the lower surface of these tuberosities, but they also occur 
in the course of the passages which communicate with the infundibulum. They measure 
about 0'006 millim. in length and 0'005 millim. in width, and have comparatively large 
nuclei of about 0'004 millim. in diameter. Some have a spot-like nucleolus, which 
in other specimens is represented only by a group of granules. Cells (fig. 21 c.) 
somewhat resembling those of the terminal row of the sixth layer of the tectum occur 
beneath the epithelial lining of the infundibulum and the ante-chamber, or ventricle 
as it may be called, of the hypophysis cerebri ; they are bipolar, tripolar, or quad- 
ripolar ; but one process, that directed away from the infundibulum, can be traced 
much further than the others ; they vary from 0'008 millim. to 0'022 millim. in 
iength, and from 0'006 millim. to 0'009 millim. in width ; they have distinct, well- 
marked nuclei, the diameter of the larger being 0'006 millim., that of the smaller 
specimens being 0'004 millim. ; in most cases the nucleolus is represented by a few 
granules, either scattered through the nucleus or collected into a group. 
In addition to these small cells, others of a much larger size (fig. 21, cl.) occur, which 
are situated more particularly under the epithelium of the ventricle of the hypophysis 
cerebri, and the adjacent anterior edge of the hypoarium ; some are pear-shaped, others 
are expanded at one end and flattened like an enlarged columnar epithelial cell, but 
they are not of the nature of epithelium, for they lie beneath that layer. The largest 
measure 0'030 millim. in length, by 0'014 millim. in width ; the nucleus is large, and 
the nucleolus also is disk-like and measures O' 00 2 millim. in diameter. 
Each hypoarium contains a peculiar spherical body (fig. 22), denominated by Fritsch 
“ nucleus rotundus.” This is placed nearer the posterior edge and the mid-line than 
the external surface and the anterior end ; it is composed of interlacing fibres and 
granules, in which are embedded cell-like bodies which differ very greatly in size, 
some measuring as much as 0'07 millim. by 0*06 millim., some as little as 0'04 millim. 
by 0'03 millim. ; many are nearly round, others longer than broad ; they are composed 
of loosely aggregated granules of about O'OOl millim. or 0'002 millim. in diameter, 
which are crowded round the circumference, leaving a space in the centre, which in 
many cases is occupied by a smooth oval or pyriform body, having somewhat the 
aspect of the protoplasm of a cell, but in which no nucleus is observable ; sometimes 
this body is missing in very thin sections, there remaining only a clear space, which it 
had probably occupied. Capillaries are occasionally to be seen passing through the 
loose granules of the circumferential portion. 
What these bodies are I am at a loss to determine ; they are of about the same size 
as the larger cells of the spinal cord. The granules also which compose their cortex 
resemble those of the protoplasm of those cells, in size and aspect, except that they 
are more loosely aggregated : they might be looked upon as cells in which the granules 
