REMARKS 
ON THE FIGURES 
OF PLATE VI. 
VERTEBRA OF THE SAME CLASS IN SERIES ARE COMPARED AMONG THEMSELVES. 
ene several classes of vertebrae which are named cervical, dorsal, lumbar, sacral, and terminal, 
do not present greater varieties of cast, compared to one another, than may be scen to characterise 
the several vertebra of one class. That peculiarity 
of design which requires us to distinguish a lumbar 
vertebra from a dorsal vertebra, or this latter from a cervical vertebra, is not greater than that which 
exists between two or more vertebre of the cervical order, between two of the dorsal, the lumbar, or 
sacral series. And hence if we are to acknowledge the reason why vertebre of the several regions of 
one series should be classified as positive distinctnesses, the like reason for classification occurs for any 
two vertebre in any one class. 
and uninterrupted design so far as their elementary 
series terminates at the caudex, we still read in that 
Slight transitional modifications of form are observable 
between vertebree of the same class, but still their elemen- 
tal pieces remain the same. 
In figs. AA” A” we represent cervical vertebrae of the 
human spine. Fig. A’ is the atlas or first spinal unit suc- 
ceeding the occiput, and although it presents itself some- 
what dissimilar to fig. A” the 4th cervical vertebra, and 
to fig. A’ the 7th cervical unit, yet still the same elements 
are to be found in all three. The modification between 
them is principally owing to the greater or lesser develop- 
ment of one or other of their elemental parts. In fig. A’ 
the atlas, that part of the centrum or body marked 4, 
becomes soldered to the axis vertebra, and forms for it the 
process named odontoid. This is one of those extraordi- 
nary metamorphoses in furtherance of mechanical fitness 
which everywhere in organic nature turns the mind to 
marvel at the design and the simple means by which such 
design has resulted. 
The figs. B’B’B” are dorsal vertebre rendered equal 
to the cervical forms by the presence of the costal elements 
a b and c, which mark the homologous parts in the cervi- 
cal vertebre also. Fig. B’ is the first thoracic or dorsal 
vertebra. Fig. B” is the 7th and fig. B” the 12th of the 
thoracic series. Similar figures indicate the homologous 
elements of each of these dorsal vertebre, and of each of 
those of the cervical order. 
The figs. C’C’C” are vertebre of the lumbar class, 
and manifest parts similar to those found in the dorsal 
and cervical order. 
In figs. D’D” D”’D”” we see the graduated propor- 
tional metamorphoses of vertebree of the sacral class. Fig, 
D’ is homologous with figs. C’B’ and A’, but when com- 
It is true, however, that all the vertebre of series constitute a whole 
parts are identical m one and all. Even where the 
minus quantity the facts of similarity. 
pared with figs. D’D’ D’”, an instance of where subtrac- 
tion from plus quantity creates the minus proportionals, 
is rendered evident. 
Still the order of metamorphoses is so carried out that 
the last caudal nodule 4, fig. D’”, refers to no other part 
of any other spinal vertebra than the centrums marked 4. 
Similar figures mark similar parts in the homologous 
forms A’B’C’ and D’, and it is also to be observed of all 
those figures, viewed comparatively, that whatever be 
their apparent modifications, still those modifications are 
happening under no other rule of development than that 
of the plus rendered minus. Fig. D”” is a minus propor- 
tional of fig. D’, this is minus proportional of fig. D”, 
and this is minus proportional of fig. D’, the first sacral 
vertebra. Hence fig. D’ beimmg equal to figs. C’ or B’ or 
A’, leaves it to be inferred that figs. D’D’D”” are 
graduated proportionals struck out of archetype quan- 
tities equal to any vertebra of series. And whilst we 
assert thus much of fig. D’”, we believe that it is as much 
within the rule of reason as if on view of a column’s 
capital cast separate and apart, we still named it to be a 
thing designedly related to a whole or column. 
We have remarked that there occur, even amongst the 
vertébree of any one class in series, such modifications of 
primitive samenesses as allow the word species to be 
applied to them as rightfully as between two vertebree of 
separate classes. The atlas vertebra is as distinct a species 
of structural design from what the seventh cervical ver- 
tebra presents, as this latter is from a dorsal or lumbar 
figure. If this be a just remark, why therefore is it that 
we designate under a common name things of distinct 
designs, such as an atlas, an axis, and a seventh cervical 
