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Aug. 11, 1870] 
NATURE 
291 
THE VERTEBRATE SKELETON 
KELETAL archetypes, and “theories of the skull,” 
have of late years gone much out of fashion, The 
view which made each man a potential Briareus as to 
limbs, seems itself to be considered as no longer having 
aleg to stand upon. The fortress of the “ Petrosal” has 
long been carried by assault, and is peaceably and se- 
curely occupied; and although we have had lately a 
brilliant passage of arms apropos of the ‘auditory ossicles ” 
from which the unlucky Sauropsida retired with broken 
“hammers” and diminished “ anvils ;” yet the once wide- 
spread interest in skeletal controversies seems to have 
long subsided. The old war-cries are no longer heard, 
the question “Is the post-frontal a parapophysis ?” falls 
on indifferent or averted ears, and we fear that even not a 
few of our anatomists call into daily functional activity 
a mandible, to the true nature and homologies of which 
they are comparatively indifferent. 
What was the surprise of some, then, who last year wit- 
nessed, in the theatre of the Royal College of Surgeons, 
an unlooked-for resurrection. Some rubbed their eyes— 
could they have had a long sleep, and was it still the year 
1849 instead of 1869? A quasi-vertebrate theory of the 
skull once more! Again an exposition of cranial hceemal 
arches ! 
“ Jam redit et Virgo, redeunt Saturnia regna.” 
But yet in justice it must be said that it was by no means 
the reproduction of an old or familiar system. The views 
propounded were in some respects as novel as striking ; 
while in spite ot this a careful re-statement of assertions 
made in the first year of the last Hunterian professorship 
showed how subordinate after all were the changes made, 
and how trifling the modifications required as to the 
statements of that first year. Nor in fact was any new 
archetypical idea of the whole vertebrate skeleton dis- 
tinctly proposed for acceptance, though the serial rela- 
tionship of certain inferior arches was clearly demon- 
strated, and a striking suggestion made concerning the 
most anterior of them. 
But some ideal conception of the vertebrate skeleton as 
a whole is a necessity for anyone who proposes to extend 
his osteological labours over several classes, and provided 
such a conception be a simple “ generalised expression of 
observed facts,” no one has a right to complain of its in- 
troduction. What best conception then of this kind can 
be now supplied from the accumulated labours of suc- 
cessive osteologists ? 
As the points of exit from the skull of the cranial nerves 
supply the best fixed points for determining special 
cranial homologies, so probably the arrangement of the 
nervous system as a whole will supply the handiest key to 
the explanation of skeletal difficulties. 
In the Hunterian Lectures of 1869, the nervous 
system was treated in a new way, and one by which the 
sympathetic system lost its isolation, and was called in to 
take its morphologically important part in the general 
system of spinal nerves. The embryonic condition being 
referred to (with ascending dorsal plates and descending 
ventral-plates—the latter bifurcating to enclose the pleuro- 
peritoneal space between their outer and inner lamin), 
each spinal nerve of the trunk was represented as sending 
one branch upwards into the dorsal plate, another 
downwards into the outer lamina of the ventral plate 
(abdominal and intercostal nerves), and another, also 
downwards, but into the inner lamina of the ventral plate, 
the collection of these latter internal nerves with their 
serial homologues forming the sympathetic system. In 
addition to these, a branch was represented as running 
directly outward towards the skin, above the external 
descending branch. Now, such being the condition of 
the nervous system, what might we a frzord expect to find 
in the skeleton? Surely we might expect to find—trst, 
Parts related to the dorsal laminze (epaxial); 2nd, Parts 
related to the external ventral lamine (paraxial), and 3rd, 
Parts related to the internal ventral laminze (hypaxial). To 
the first category would belong the neural arches, &c. ; to 
the second, the transverse processes, ribs, and steruum ; to 
the third would belong those skeletal structures, if such 
there are, within the pleuro-peritoneal cavity or medianly 
situated beneath the vertebral column. 
But as to the nerves passing directly outwards above 
the external descending ones, are there any skeletal 
structures to answer to them ? 
Now, fishes present us sometimes with a double series 
of ribs, whereof the upper strike out towards the skin, 
while the lower tend to enclose the abdominal cavity. 
In tailed Batrachians we have two superimposed trans- 
verse processes to which a bifurcating Y-shaped rib arti- 
culates, and this rib sometimes bifurcates distally also. 
In mammals we have a rib essentially similar as to its 
proximal end, but one branch of the Y is diminished 
into a tubercle which, however, meets a transverse pro- 
cess. Can it be,then,that our own ribs are morphologically 
double, and that their upper proximal parts together with 
the fascia ascending from them to bound externally the 
erector sping, are homologous with the upper series of the 
ribs of fishes ? 
But what are the hypaxial structures, and first, what 
parts of the skeleton are within the pleuro-peritoneal 
cayity or are serially homologous with parts so situated ? 
Here an important modification seems necessary in the 
views given out by Professor Huxley in 1869. He de- 
monstrated unanswerably that the branchial arches are, 
as Professor Goodsir considered them, thoroughly homo- 
logous with the hyoidean and mandibular arches, and not 
only this, but he also suggested—what was as novel as 
important—that the ¢vadecul@ craie may be the foremost 
members of the same group of parts. He considered, 
however, that all these parts were cos¢ad in their nature. 
Now, accepting this view as far as regards the serial 
homology of the branchial arches with parts more an- 
terior, it is nevertheless here submitted that the branchial 
arches should be considered parts wéthzm the pleuro- 
peritoneal cavity, and this because the heart lies owtside 
them, and the great vessels {which even in man have 
reflected on them a continuation of the pericardium) 
extend along their ow/er sides. It is contended, then, 
that these arches are hypaxial parts, and, if this is so, 
then the hyoidean, mandibular, palato-quadrate, and 
trabecular structures, as they are serially homologous with 
the branchial arches, must be hypaxial also. If so, the 
nerves which accompany them (the vagus, &c.) must be 
serially homologous with the sympathetic nerves of the 
trunk, and, indeed, this view was put forward by Professor 
Huxley in the lectures referred to, Are there, then, no 
