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On the Anatomy of the Nervous System in the Lumpricus 
TERRESTRIS. By James Rorin, M.D. 
Up to avery recent date, anatomists have generally re- 
garded the nervous system of the Insecta, Mollusca, and 
Annulosa, as consisting of a structure essentially different in 
its microscopical characters from that of man and the higher 
mammalia generally. The nerve centres of these animals, 
for imstance, have usually been considered as composed of 
unipolar cells, from which minute fibres arise and pass di- 
rectly to the muscles and organs supplied. That such an 
arrangement is the correct one has, however, now been called 
in question, not only on anatomical but also on physiological 
grounds ; for if we admit that these nerve-cells are unipolar, 
then we must also admit that each cell is a separate nerve 
centre having no connection or relation with its neighbouring 
cells. This view, while opposed to all analogy, will be shown 
by the following notes to be equally opposed to correct obser- 
vation. It is not, however, to be wondered at, that such a 
view should have been so generally received. On examining 
the nervous system, particularly of the Insecta, the appear- 
ance of unipolar cells is often presented, and it is only by very 
careful management of the light that a correct knowledge of 
the arrangement of the nerve-cells and nerve-fibres can be 
arrived at. In the present paper I propose to consider the 
anatomy of the nervous system of the common earth worm, 
(lumbricus terrestris,) because it presents to our view a 
nervous system of a very simple form, and especially because 
on account of its small size and transparency the different 
ganglia can be examined entire without our being obliged to 
have recourse to sections. 
General anatomy.—In the Lumbricus terrestris, the nervous 
system may be considered as consisting of two parts, a supra- 
cesophageal portion and a ventral or infra-cesophageal portion. 
The former or supra-cesophageal portion consistsof two small 
spheroidal ganglia, situated immediately over the mouth of the 
animal, and connected together by ashort commissure. From 
each of these ganglia a band of nerve-fibres pass downwards on 
either side of the cesophagus, and become attached to the first 
of the ventral or infra-cesophageal chain. The only nerve given 
off from this portionof thenervous system, is “‘a simple nervous 
filament,” which, according to Brandt, “‘is continued from 
the cesophageal ganglion along the dorsal aspect of the 
alimentary canal,” and which is by Owen considered to be 
