272 Bibliographical Notices. 
example of what is almost universally regarded as connective tissue.” 
Concerning the relative development of white and grey matter, it is 
seen that there is more white matter in the brachial region and 
more grey matter in the crural region of the frog. And since the 
length of the lumbar enlargement is to the cervical enlargement as 
10 to 6 in the frog, it is evident that the grey matter is much more 
abundant in the lumbar region. Long-tailed Saurians like iguana 
and the alligator have the white and grey substances nearly equal 
at both enlargements; but those with short tails have the cervical 
enlargement more developed. Chelonians usually have no large 
nerve-cells in the inferior horns of the grey matter. In the gopher, 
multipolar and bipolar cells occur, which are similar to those seen 
in enlargements of the spinal cord in reptiles. Nerve-cells with 
nuclei, though abundant, only form a distinctly defined group in 
the Hora region of the frog, above the level of the central canal, on 
each side of the substantia reticularis. In the frog the axis-eylin- 
ders of the inferior nerve-roots can be followed into the grey matter, 
and become lost in the large cells. These are the more important 
conclusions which the author formulates ; but the materials which 
are represented in the plates make it manifest that a reticence and 
modesty have been shown, which throw a good deal of labour upon 
the reader in efforts to generalize where the author would probably 
have been more successful. 
The spinal cord passes very gradually into the medulla oblongata, 
where the central canal and inferior commissure in Saurlans occupy 
a lower plane, though in the alligator it rises and opens into the 
ventricle. Here the raphe appears, and extends as far forward as 
the substance which corresponds to the pons Varoli. In the meshes 
of the raphe are nerve-cells which extend forward, till just behind 
the plane of the auditory nerves they become the largest cells of the 
nervous system. Similar cells occur in skinks, anolis, heloderma, 
iguana, and all Saurians which have the raphe well developed. On 
each side of the raphe cells are arranged in three groups, which 
have been called nucleus basilaris, nucleus centralis, and nucleus 
lateralis. The nucleus centralis includes superior and inferior divi- 
sions. The author observes that this centre in the crocodile may be 
related to the vagus; but adds that it is perhaps more probable 
that the cell-column which extends from the anterior bundles of the 
spinal accessory to the anterior bundles of the vagus contains all 
the cells in which both the vagus and hypoglossal nerves originate, 
the reason for this doubt being that the roots of the hypoglossal 
nerve have not been traced. ‘The origin, however, of the abducens 
nerve is evident in all the reptiles examined ; it lies in the floor of 
the ventricle, and is well seen in section. 
The cells connected with the auditory nerves show many varia- 
tions in the different animals. In the frog the motor bundle of the 
trigeminal nerve is seen in cross sections, though it is more easily 
demonstr ated in true reptiles, and is well ‘shown i in a section of the 
medulla oblongata of the alligator. 
The cerebellum is represented by longitudinal vertical sections. 
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