THORACIC TRUNCUS SYMPATHICUS 429 
the lower eight thoracic white rami turn downward toward the 
splanchnic nerves, and accumulate in the trunk. It is probable 
that many of them branch on their way down. Langley (’00) 
states that the large fibers of the sympathetic system occasionally 
divide. In this case the branches are of somewhat less diameter 
than the parent fibers. He does not state how these observations 
were made, but most of his histological observations were made 
on teased preparations. As evidence that division of the large 
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Fig. 6 A small part of a section of the eleventh thoracic internodal segment 
in the cat. Osmic acid. X 425. 
fibers occurs in the sympathetic trunk we may mention the results 
of the enumeration of the large fibers in the lower thoracic white 
rami and in the trunk just above the origin of the first splanchnic 
nerve. Only fibers 6u or greater were counted. The total num- : 
ber of large fibers in the lower eight thoracic white rami was 
864. In the trunk just above the origin of the first splanchnic 
nerve there were 464, i.e., a little more than half'as many as in 
the rami. Since, as we shall see, all or practically all of- the 
large fibers from these rami turn downward in the trunk, and 
since none or almost none are given off in any of the other 
