466 EDGAR J. ALLEN, 
of the cord, giving off a fibre which runs anteriorly to the 
brain. 
C. Elements (fig. 4 red) made up of a cell in one ganglion, 
and a fibre which runs posteriorly and ends in the next gan- 
glion of the cord. 
D. Elements (fig. 4 blue) made up of a cell in one of the 
ganglia of the cord and a fibre which runs anteriorly, giving 
off collateral branches in the next ganglion, and ending in the 
next ganglion but one. 
\ A. 
\\ These elements are represented in fig. 2. In this figure 
only cells of the left side have been drawn, but exactly similar 
elements exist starting from cells on the right side. The 
figures 1—4 are necessarily somewhat diagrammatic, but in 
almost all cases the individual elements are drawn from actual 
preparations, and I have endeavoured to make the diagrams 
represent as nearly as possible the actual appearance of pre- 
parations. 
The elements of this class, for reasons to be explained, must 
be regarded as only placed provisionally in Group I. It may 
be necessary subsequently to place them in a group by them- 
selves. Two kinds of A elements may be distinguished—(a) 
those whose fibres decussate (blue in fig. 2), and (4) those 
whose fibres pass down on the same side of the cord (red in 
fig. 2). 
Staining of the following elements of this class has been 
obtained :— 
A (a) Br.—A pair of elements each consisting of a large 
cell on the ventral surface of the brain, from which a moderately 
thick fibre at first runs forwards and upwards to the dorsal 
surface. After turning outwards the fibre runs backwards to 
a point immediately in front of the cesophagus, where it passes: 
across to the other side and runs down the ganglionic cord. 
On entering the first thoracic ganglion the fibre becomes very 
broad, having a diameter many times greater than that of any 
other fibre in the body, and, maintaining this exceptional size, 
