2 REMARKS ON THE FIGURES OF PLATE XIII. 
one vertebra of series symmetrically formed gives this 
character of symmetry to them, one and all. The spinal 
axis, viewed as a whole, is symmetrical, and so is any 
vertebra of series. The symmetry of the unit of series 
implies the symmetrical condition of the whole series. 
In fig. A we say that every vertebra of such series holds 
At the cervix of fig. A we see that 1 
is the homologue of that piece marked 2, in the dorsal 
class, also of the piece marked 3, in the lumbar region, 
and of the piece marked 4, in the sacral class. Those 
pieces are the exogenous transverse processes, and are 
identical elements. 
severally developed from those primary nuclei common to 
them and the laminz of the neural arches. 
In fig. B we also discover that similar elements are to 
be found in all the vertebre of series, for the piece marked 
a, at the cervix, is the homologue of the piece marked 6 
at the dorsal region, also of the piece marked c¢, in the 
loins, and of that marked d in the sacral region. Those 
pieces are the autogenous elements located in front of the 
exogenous transverse processes. Those autogenous ele- 
ments a, 6, c, and d, are undoubtedly homologues of each 
other, and it matters not what name we. give them; it 
matters not whether we call them transverse processes at 
the cervix, cost at the dorsal region, transverse processes 
at the loins, and lateral masses at the sacral spine, for 
they are still identical elements. 
As the perpendicular median line of cleavage divides 
the spinal series into identical halves, and passes through 
the common centre of all the vertebra from occiput to 
caudex, so may it be said to sunder the created plus forms 
of vertebre ranging between occiput and the first sacral 
vertebra; whereas this median line only severs the minus 
proportionals of the like vertebree in those figures of sacral 
and coccygeal order. It is sufficient that we understand 
the last caudal ossicle to be the centrum of a metamor- 
phosed vertebra. 
The horizontal line 5, which passes through the dorsal 
region of the vertebral series, may, therefore, be said to 
divide the series of forms, which are all homologously 
developed above and below itself. The cervical vertebra 
contains elements the same as that. vertebra standing at 
dorsum, loins, or sacrum. . 
Bilateral symmetry, which we observe to characterise 
the mammalian spinal axis, necessarily occasions an in- 
quiry as to how it exists, and upon what other conditions 
of development it is dependent. 
those created serial forms upon which the law of symmetry 
attends there can exist any absolute difformity—and if 
there be such, how it can happen that the common 
character of symmetry should thus enchain uniformity and 
difformity in one continuous line. In the mammal spinal 
axis we discover the result of three relationary laws, all 
combining to a harmonious effect, and because their several 
One of those 
laws is symmetry, the other is series, the third is propor- 
operations are in harmony with one another. 
Whether in the order of | 
tioning, and the figure which is created under their joint 
operation is the mammalian spinal column. 
When we examine the acts of nature as to the creation 
of things in symmetry and in serial order, we find those 
acts to be based upon uniformity absolute and per se, upon 
a uniform operation so totally isolated from diversity, that, 
considering the former as existing, we may account the 
latter as null and void. For we find that a form which is 
symmetrical is an existing evidence of nature repeating her- 
self in developing one side after the plan of the other, and 
thus by the uniform act giving rise to a uniform creation— 
that is to say, to a thing of symmetry equal as to its sides. 
Again, when we question nature as to her creation of 
serial order which those things of symmetry assume one to 
the other, we find that this is also founded upon uniformity 
or the repetition of one quantity in another, and this in 
the next. The first creation of a symmetrical unit, such 
as a vertebra, will, when repeated again and oftener 
through a serial line, be resulting not only in serial sym- 
metry but in serial uniformity—and so the result of both 
laws is a simple multiplication of a first design. The law 
of symmetry and the law of series are uniform operations, 
and are hence productive of uniform, equal, and homologous 
forms and quantities. * . 
Still, however, we find that the mammalian spinal axis, 
although equal and symmetrical as to sides, isnot uniform 
as to the several quantities of series—and hence arises the 
question as to how the series exists symmetrically, at the 
same time that we must acknowledge the series to be one 
of unequal quantities at its sacro-caudal termination. 
This question is answered by the very facts of the case ; 
itself. For, while we know that series terminates by process 
of proportioning, or the subtraction from plus quantities, 
and that a caudex is only various to other regions of series, 
Just as minus is various to plus, we then clearly understand 
that process which fashions the caudal series as a special 
design and fitness from out of plus quantities equal to 
those elsewhere occurring in the same series. We still 
find that symmetrical formation is characterising a caudal 
Wealso find that caudal modification holds in the 
same continuous serial order with all the plus quantities, 
series. 
that the one common median line bisects the whole series 
of plus and minus figures, and hence we infer that the only 
variety between these quantities of the one serial line, is 
that resulting by the law of proportioning, and that this 
law has acted symmetrically by the degradation or sub- 
traction of quantities equal from one unit at both sides of 
its median line, and graduatedly for succeeding units at 
both sides of their median line down to the last caudal 
bone. 
And herewith, under the above interpretation, it will 
occur that while we bisect series in figs. A and B from the 
atlas vertebra to the last caudal bone, we cleave in the 
latter minus quantity the actual centre of a figure meta- 
morphosed symmetrically from a plus quantity, or whole 
* Tam miram uniformitatem in planetarum systemate, necessario fatendum est intelligentia et concilio fuisse-effectam. Idemque dici possit 
de.uniformitate illa que est in corporibus animalium.—Newton.—Optice, sive de reflex., &c. p. 411. 
