168 J. B. Johnston 
the preparations entirely reliable for this purpose. Two things sug- 
gest the probability of such connections: first the fact that the 
dorsal rami of the spinal nerves pass close to this nerve; and se- 
cond, the faet that the lateral line nerve is considerably thicker 
opposite the dorsal spinal nerves. 
The value of the second point will appear from a few obser- 
ations transcribed from my study notes. 490, Z.l. nerve very small 
and compact, fibers fine. ÖOpposite a motor root. Muscles seem 
to crowd it. 509, nerve large, fibers thick. Spinal ganglion beneath 
and vessels lie between it and muscles. 522, extremely small 
and compact. Surface of cross section not more than one-fourth 
as large as in 509. Even smaller in the sections following, direetly 
over a motor root. 550, in an intersegmental space with a spinal gang- 
lion, nerve very large. 570, 
over a motor root, small. The 
differences in diameter of the 
nerve resolve themselves into 
a very simple matter. In each 
intersegmental space where the 
spinal ganglia lie the nerve has 
plenty of room and the fibers 
are large and not closely packed 
together. In the middle of each 
myotome tbe nerve is pressed 
upon by the muscles and not 
only are the nerve fibers closely packed together but they are greatly 
reduced in volume. It was my intention to count the number of 
fibers in the nerve opposite a spinal nerve and the number between 
two spinal nerves, but this proved impossible as well as unnecessary. 
ÖOpposite the spinal nerves the most of the fibers are very large and 
it would be quite easy to count them, but in the middle of a seg- 
ment the nerve is so compact that it is useless to attempt to distinguish 
individual fibers (see Fig. 16). 
I have followed the lateral line nerve carefully from its ganglion 
to a point behind the twelfth dorsal spinal nerve and find no con- 
nection with any of these nerves. The nerve always has a strong 
sheath and although some of the ganglia and dorsal rami of the 
dorsal nerves lie close against the lateral line nerve, the sheath of 
the latter remains intact and no fibers enter or leave the nerve. In 
some cases the dorsal nerve is completely separated from the lateral 
