6 ALBERT KUNTZ 
the aorta which could be interpreted as the primordia of the 
sympathetic trunks. Neither do aggregates of cells occur along 
the ventrolateral aspects of the aorta which could be interpreted 
as the primordia of the prevertebral sympathetic plexuses. Fig- 
ure 2 is taken from a section through a lumbar segment somewhat 
farther cephalad. In this segment a remnant of the ventral 
portion of the neural tube persists from which a slender ventral 
nerve-root without visceral efferent fibers has grown out unilat- 
erally. This section shows the same absence of the primordia 
of the sympathetic trunks and the prevertebral plexuses as the 
one illustrated in the preceding figure. These sympathetic 
primordia are absent also in all the intervening sections, although 
sections through the corresponding segments of normal embryos 
representing the same stage of development show an abundance 
of cellular elements both in the primordia of the sympathetic 
trunks and the prevertebral plexuses. In the embryo from which 
figures 1 and 2 are taken the primordia of the sympathetic trunks 
are absent in at least eight successive segments. Other embryos 
of the chick in the present series show the same absence of the 
primordia of the sympathetic trunks in all segments in which the 
peripheral migration of cells of nervous origin was prevented by 
early operation. If the sympathetic were not genetically related 
to the cerebrospinal nervous system, but differentiated in situ, 
the primordia of the sympathetic trunks ought to be present in 
segments in which the cerebrospinal nervous system is absent 
as well as in segments in which the latter is normally developed. 
Embryos of the frog in which the neural crests and the neural 
tube were extirpated,posterior to the cephalic region before any. 
peripheral migration of nervous elements had taken place also 
show complete absence of the primordia of the sympathetic trunks, 
although such primordia are present in unoperated embryos 
representing the same stage of development. This observation 
is not new. In embryos of the frog from which a strip of tissue 
including the neural crests and the neural tube was cut early 
throughout the greater part of the trunk, Harrison (04) ob- 
served that ‘‘distal to the point of termination of the intrinsic 
fibers of the cord there are no nerves of any description in the 
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