HISTOLOGICAL NOTES. 
477 
central nervous system approaching too close from side to 
side, and consequently the central canal becoming alto- 
gether lost. A.nd this state, viz. the shutting-up of the 
central canal, forms one of the most troublesome impedi- 
ments to see the cilia and their movement. In embryos of 
a later stage the examination proves unsuccessful, partly 
owing to this collapse of the central canal, but chiefly to 
the relative opacity of the tissue, an opacity far too great to 
allow the very delicate cilia to be perceived. In embryos of 
an earlier period, such as possess only about 6 — 10 proto- 
vertebrse, I could not detect either the ciliary movement or 
the cilia themselves, although in several instances the 
central canal had not collapsed. 
In the central canal of the earlier embryos, as well as in 
those of the later ones, there were always to be met with a 
few spherical or oval, coarsely granular, and therefore 
opaque, corpuscles, either isolated or two or three together ; 
they varied in size, and a nucleus could not be seen in 
them. 
In transverse sections through the above hardened embryos 
nothing of the cilia could be seen, but this will nOt surprise 
since the cilia of less delicate structures are lost during 
hardening ; one of the best known examples is the mucous 
membrane of the human uterus, and of that of mammals, 
III . — The Glands of the Nasal Cavity of the Guinea-pig. 
As is now well known, the glands occurring in the mucous 
membrane of the nasal cavity are mucous and serous glands 
(Heidenhain). The latter form, in the thick portions of the 
non-olfactory Schneiderian membrane, huge masses, in which 
the alveoli — convoluted tubes, with lateral and terminal 
shorter and longer branches— are grouped into lobules, 
separated, as in other cases, by vascular connective-tissue 
septa. 
The alveoli of the mucous glands present themselves 
in two different forms : either small, with a small lumen and 
lined with polyhedral or short columnar cells, each with a 
spherical nucleus; or large, with a large lumen, -and lined 
with columnar cells of the nature and aspect of mucous 
cells. T here are alveoli in which the two kinds of cells occur 
side by side. Thus, .they resemble the mucous glands of the 
larynx known through Heidenhain, Tarchetti, myself, and 
others. The ducts are lined with a single layer of . thin 
columnar cells, as in other mucous glands. At the com- 
mencement of the nasal mucous membrane, i, e. near ,the 
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