176 JULIA WORTHINGTON. 
The Second Spino-occipital Nerve.—This second 
spino-occipital nerve is similar, in some ways, to the first, in 
other ways it is more like the purely spinal nerves that follow 
it. It also arises from the transition region between brain 
and cord. It has one sensory and four motor roots, which 
belong, however, to two main stems, of two roots each, cor- 
responding to the two motor roots of the spinal nerves. In 
this nerve, aS in the following ones, the motor roots are 
cephalad of the sensory ones. The sensory root passes out 
through its single foramen to the ganglion, the motor roots 
are variable on the right side of one specimen examined 
passing through two foramina, and on the left side uniting 
inside the wall and passing as a single trunk. It must be 
noted that in all the spinal nerves, however, the motor roots 
emerge from the wall as a single trunk, the separate foramina 
having run together and united before the lateral face of the 
wall is reached. ‘lhe motor root, as in the case of the first 
spino-occipital nerve, runs ventrad of the ganglion, joining 
the sensory root as it emerges therefrom. The nerve then 
runs cephalo-caudad for a space, like the first spino-occipital, 
then turns ventrad, running on the inner face of the lateral 
body muscles. Unlike the first spino-occipital it does not 
divide into two branches until near the ventral surface. 
The First Spinal Nerve.—This nerve is the first to 
arise from the region of the spinal cord proper beyond the 
area of transition, and there are other features about it 
that distinguish it sharply from the two nerves preced- 
ing. It has one sensory and two motor roots. As in all 
the spinal nerves, the motor roots pass the wall by a 
Y-shaped foramen, and emerge as one trunk. Jt is outside 
the wall that a striking difference is seen between this nerve 
and those that have gone before, for the spinal nerves supply 
the dorsal as well as the latero-ventral skin and muscles. 
The ganglion, instead of being a spherical or ovoidal cluster 
of cells, is elongate, with two arms, a dorsal and a lateral. 
The dorsal arm, running upwards outside of the sheath of the 
spinal cord, gives off the dorso-sensory branch of the first 
