. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 411 13 having been noted by Froriep in Torpedo. The posterior 3 or 4 have ventral roots corresponding to them, and the last may possess a rudimentary dorsal ganglion in man and mammals. The last four in the gull have rudimentary dorsal roots, and Chiarugi described rudimentary roots to the posterior three in Gallus. There are similarly 3 to 5 in reptiles, which have apparently no dorsal roots. A dorsal ganglion has been discovered also to the last nerve of the three which may survive in Selachii. Even the first spinal nerve m
. Anatomischer Anzeiger. Anatomy, Comparative; Anatomy, Comparative. 411 13 having been noted by Froriep in Torpedo. The posterior 3 or 4 have ventral roots corresponding to them, and the last may possess a rudimentary dorsal ganglion in man and mammals. The last four in the gull have rudimentary dorsal roots, and Chiarugi described rudimentary roots to the posterior three in Gallus. There are similarly 3 to 5 in reptiles, which have apparently no dorsal roots. A dorsal ganglion has been discovered also to the last nerve of the three which may survive in Selachii. Even the first spinal nerve may in like manner to those in front lose its dorsal ganglion and root in man and mammals. The seven which I have described above appear to be identical in number and position with the seven which Sewer- TZOFF discovered in Ceratodus. It is at once evident therefore that if these ventral roots of the occipital somites are posterior to the cranial nerves and the latter. Rudimentary dorsal roots -dorsal ganglion Fig. 4. A similar reconstruction from sagittal sections of the still older embryo, '62'. are homologous with the dorsal roots of the spinal nerves we must find room for a minimum of 13 nerves and neuromeres behind the vagus, which would yield 21 rhombomeres and still more if the com- plex condition of the vagus be considered. There is evidence to show however and it has been stated before, for instance by His in 1888, that the cranial nerves are not homo- logous with the spinal dorsal roots. The latter pass internal to the myomeres to join the ventral roots, are not connected by ganglia with the ectoderm, and are segmental in position. The cranial nerves, with the exceptions which will be mentioned, pass outside the myotomes, characteristically establish ganglionic connexions with the ectoderm (the lateral line and epibranchial system), are independent of the ventral roots, and are intersegmental in position. The two classes of. Please note that these images are extracted
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