656 
fibrous substance, and that it is applied from 
Within outwards on the surface of this latter. 
Consequently, the opinion of M. Gall, that it 
is formed prior to the medullary, and is, as 
it_ were, the matrix, is absolutely false with 
regard to the spinal marrow, for we already 
perceive the roots of the spinal nerves, in 
the second and third months, although at this 
period there is no cortical yet deposited in its 
canal.” 
* It is very remarkable that the canal ofthe 
Spinal marrow exists constantly and during the 
entire life of the animal, in fishes, reptiles, and 
birds. I have met it in a great number of 
fishes, both of salt and fresh water, such as 
the ray (Raia), shark (Squalus), bream 
( Cyprinus brama ), bandfish ( Cepola), pike 
( Esox ), salmon, carp, &c.; and I have always 
found its internal surface covered with a layer 
of grey substance. The observations of M. 
Arsaky agree perfectly with mine in this re- 
spect.””* 
“ I have observed the same canal, in ques- 
tion, in the hawk’s-bill tortoise, common tor- 
toise, a young crocodile of the Nile, wall li- 
zard, ringed snake, land salamander, green 
frog, and the common toad. In front it is 
continuous with the fourth ventricle, or rather 
it dilates to give origin to this cavity, and its 
interior was covered with a thin layer of cortical 
substance.” 
“ Birds possess this canal both in their 
embryo state and in adult age. In these it 
forms, at its inferior part, a remarkable exca- 
vation, which Steno, Perault, Jacobceus, and 
some other authors have described under the 
name of the rhomboidal sinus. In birds, also, 
the grey substance occupies the interior, and is 
no where in greater abundance than on the 
walls of this sinus.” 
“ The canal equally exists in the spinal mar- 
row of the fetus of mammiferous animals, as 
also in the young animals of this class (?) F. 
Meckel has found it in the embryo of the rab- 
bit;+ and G. Sewell in young animals of the 
genus dog, sheep, ox, and horse.{ This latter 
writer observes that it was filled with a colour- 
less fluid, nearly opaque, and of the same na- 
ture as that which existed in the ventricles. 
F. Meckel has even meta small canal full of 
fluid in the spinal marrow of some of the adult 
mammiferous class, such as the dog, cat, rabbit, 
sheep, and ox. Blaes has met it also in many 
adult mammiferous animals. 
“ Although we cannot find this canal in the 
spinal marrow of the human adult in its nor- 
mal state of developement, still it has undoubt- 
edly been met with; we should, then, consider 
it as the result of a retardation in its develope- 
ment. Charles Stephen§ was the first who 
gave a description of it; and Columbo,|| Pic- 
* Diss. de piscium cerebro et medulla spinali. 
Halle, 1813, p. 9. 
+ Beitriige zur Vergleichend: Anatomie, cap. ii. 
No. i. p. 32. 
+ Phil. Trans. for 1809. 
§ De dissectione partium corporis humani, lib. iii. 
Par. 1545. 
De re anatomica, Ven, 1559. 
NERVOUS SYSTEM. (Nervous Centres. Tue Sprvat Corp.) 
colhomini,* Bauhin,+ Malpighi,t Lyser 
Golles,|| Morgagni,4 Haller,** and M. Portal, 
have since observed it. Many of these write 
have even considered it as a constant and ne 
mal disposition; an hypothesis which Varol 
Monro, Sabatier, and some other anatom 
have justly opposed. Nymman procees 
even still further, for he spoke of two ca 
prolonged into the spinal marrow. Gall) 
tends to have found in the spinal marrow 
new-born infants, in infants of a certain 
and even in certain adults, two canals | 
from all communication with the fourth 
tricle, but which extended through the } 
Varolii,the tubereula quadrigemina and the n 
dulla oblongata into the interior of the a ptic 
lami, where they formed a cavity sufficient 
lodge an almond! These two supposed cana 
with their termination in the optic thalami, 
not exist; we must suppose that they are ] 
duced by a forced insufflation: I have ne 
met them either in the adult or in the foe 
nor do we find them in animals in which 
canal of the spinal marrow always comm 
cates with the fourth ventricle, by means 
the calamus scriptorius.”’ tf 4 
We shall notice further on the recent si 
ment of Stilling and Wallack on this subje 
Bloodvessels of the spinal cord.—The art 
of the spinal cord are derived from the vi 
bral arteries as well as from the small ve 
which ramify upon the spinal column i 
cervical, dorsal, and lumbar regions. = 
Of these the largest and most importat 
the two spinal arteries which spring fron 
vertebral on each side, distinguished as 
anterior and posterior spinal arteries. 
The anterior spinal artery is the larger 0 
two. It arises from the vertebral artery ne 
the basilar: sometimes it comes from the 
silar itself, or from: the inferior cerebellar; % 
sometimes the arteries of opposite sides 
different origins, one arising the vel 
and the other from the basilar. It passes 
vertically downwards, inclining inwards, it 
of the medulla oblongata, and having 
for a short distance in front of the e 
unites at an acute angle with its fellow 
opposite side, forming a single vesse 
passes down in front of the anteric 
fissure, under cover of the band of white 
tissue which is found along the middl 
anterior surface of the cord. The arte 
formed is called the anterior median ari 
the spinal cord. 
“« The anterior or median spinal arter 
Cruveilhier, “ therefore, results from th 
at 
* Anatom. Przlectiones, Rom. 1586._ 
+ Theatrum Anatomicum. Francf. 160 
t De cerebro, in his Opera Minora, t. ti 
§ Culter Anatomicns. Copsanas: HSS. 
KT de l’ceconomie du grand et petit 
4 Adversar, Anatom. Animady. xiv. — 
** Elem. Physiologie, t. iv. a 
tt Observ. sur un spina bifida et sur le! 
ies epiniere ; dans Mém, de l’Acad, 
tt Dr. Bennett’s translation of Tiedemam 
tomy of the Fetal Brain, pp. 124 et sqq. 
