REMARKS ON THE FIGURES OF PLATE XIII. 
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THE UNIFORM VERTEBRAL SERIES POSSESSES A BILATERAL SYMMETRY. 
(fe a series of quantities, each of which might be termed absolutely equal, uniform and pel 
throughout, we would expect to find the first quantity equal to the last, and both equal to all the rest. 
Such is not the case with the mammalian spinal axis, for in it we see an example of how the law of series 
is greatly modified by the law of proportioning, which latter renders the former finite as to the figures of 
its creation. When we contrast the operation of the law of series with the law of proportioning we then 
contrast original uniformity with proportional variety, and such is the character attaching to the mammal 
spinal axis, which evinces a creation under both influences. The development of an absolutely uniform 
and symmetrical series of equal vertebral quantities, would have produced, at the caudal termination, 
figures in plus character, and equal to those which we find persisting at the lumbar, dorsal, or cervical 
regions of ‘the same series, The supposition of such a cast of formation at once describes the fact of 
unfitness, although the cast would be that of uniformity throughout the series. But when we contrast this serial 
uniformity with the actual condition of figures displayed in the spinal axis, we then hold comparison between 
the form as it is and the form from which it has been proportioned, and hence estimate its present fitness 
with its original unfitness. Hence we know that the mammal spinal axis is na existing as a fitness 
produced by the operation of three combined natural laws, one being that of symmetry, the other being 
that of serial uniformity, the third being that of. proportioning. Hence we say that the latter modifies 
the creations of the two former, and terminates series at the caudex by the subtraction of elements. But 
this subtraction, or proportioning, takes place, for the most part, symmetrically. 
Every vertebra of the spinal series is cleavable, through 
its median line, into symmetrical sides. Those sides con- 
tain, as we have before seen, identical elements. The one 
side of a cervical form is similar to its opposite. The 
same remark applies to the vertebra of dorsal cast, 
to that of the lumbar, and to that of the sacral form. 
Moreover, we have seen that the vertebre of cervical, 
dorsal, lumbar, and sacral forms, contain the like number 
of homologous elements, consequently all the vertebra are 
homologues, and the one is representative of the other 
and of all others. We do not pretend to say that the last 
caudal ossicle is equal to any vertebra of series; this 
assertion would at once appear absurd. But we only say | 
that it is a minus quantity compared with the vertebral 
plus quantity, and that this caudal ossicle is a vertebral 
centrum, holding series with all other vertebral centrums. 
We name the caudal ossicle to be a centrum, and this 
amounts to the same thing as if we called it the centrum 
- of a vertebra, which it really is, and so we say of it that 
it has been metamorphosed from a vertebra equal to any 
other. 
Now all those vertebrze of series are related to one 
another by the fact, that the common line of median 
cleavage passes through them one and all from occiput to 
the terminal caudal nodule. 
Fig. A is a back view of the human spinal series, and 
the common median line passing from the vertex 6 to the 
terminal caudal ossicle, renders bipartite all the vertebral 
forms. This line severs them all behind through the 
spinous processes, and leaves the one side of series homo- 
logous with the other. ; 
Fig. B is a front view of the same spinal series, and in 
it we see that the same median line has passed through 
all those homologous vertebrz at their centrums or bodies, 
from the first vertebra named atlas, to the last named 
caudal ossicle. 
The law of symmetry is thus seen to prevail for the 
entire skeleton axis. The same law which renders any 
