38 EDGAR J. ALLEN. 
and vi. The element R, Th. v1, shows their principal cha- 
racters. The cell in this case lies in the posterior portion of 
the central mass of ganglion cells of Th. v1.1 It is somewhat 
smaller than the cell of the element Q, and its fibre runs 
forwards for some distance before turning outwards. After 
proceeding in the outward direction, the fibre again turns 
forwards and runs into Th. v, leaving the central nervous 
system by the posterior root of that ganglion. Two principal 
branches are given off during its course, one arborescing in 
the neuropile of Th. vi, the other in that of Th. v. 
Another pair of elements, whose cells lie in one ganglion 
whilst the fibres pass out through the posterior roots of the 
ganglion in front, is that lettered S in Th. x1 (fig. 1). In this 
case, however, the elements of the opposite sides decussate, 
giving rise to the characteristic figure shown (fig. 1). The 
cell of this element is small, and lies on the central surface of 
the ganglion. The element occurs also in the abdominal 
ganglia, and will be subsequently described in more detail. It 
has not stained in any other ganglion of the thorax, except 
Th. x1. 
ELEMENTS HAVING TWO OR MORE BRANCHES WHICH PASS OUT 
OF THE CENTRAL NERVOUS SYSTEM BY THE NERVE-ROOTS OF 
DIFFERENT GANGLIA.—T wo pairs of elements of this kind have 
stained in the thorax, the cells of one pair being found in 
Th. vir, those of the other in Th. vi1rt. In the latter case 
(Fig. 1, T, Th virz) the cell les in the anterior portion of the 
lateral mass of ganglion cells, near the point at which the 
anterior nerve-root leaves the ganglion. The cell gives off a 
moderately fine fibre, which very soon bifurcates, one branch 
passing immediately out of the ganglion through the anterior 
nerve-root, whilst the other runs forwards along the ganglionic 
cord. The forward branch, keeping close to the lateral masses 
1 As was mentioned in Part I (see this Journal, vol. 36, p. 465) the central 
masses of ganglion-cells of the embryo, shaded blue in fig. 1, divide at a later 
stage into an anterior and a posterior portion, the two portions belonging to 
two adjacent ganglia. The line of demarcation is seen in Th, IX (fig. 1). 
