REMARKS ON THE FIGURES 
———S 
OF PLATE II. 
SIMILAR PARTS ARE SUBTRACTED FROM SIMILAR VERTEBRAL QUANTITIES. 
Vy aes from equal things we take away equal things, respectively, the remainders will be equal. This 
iS an axiom in geometry, and without a doubt applies also to comparative osteology. The creation 
of form must be through the agency of a law of development, and this law being uniform in its operation, 
must create figures uniform and homologous as to quantity. We say the creation of plus forms by a 
uniform law must be the repetition of plus form and quantity, but we by no means assert that all forms are 
created equals as to quantity. When two or more figures of one species or cast are created in full 
quantity, those figures are developed uniformly. When these same figures are varied from one another, 
the variation takes place by the non-creation or omission of certain elementary parts. The variation of 
form is plus and minus. The form of plus quantity is positive, the form of minus quantity is negative. 
Plus quantities are uniform, being positive creations. Minus quantities are various to plus quantities 
solely on account of the subtraction of elementary parts. The law of form appears to be one of addition 
and subtraction of elementary parts, and therefore the forms themselves must vary according to the 
presence or absence of certain quantities. For which reason it becomes impossible rationally to name 
plus and minus quantities (of one species, such as vertebre) to be absolutely homologous or equal. 
Equal quantities are uniform and homologous ; unequal quantities are different to these only by reason 
of the subtraction of parts. And the comparison of equals and unequals, or plus and minus quantities, 
will show how much the latter are minus compared with the former or plus, for it is true that 
we see in plus those very same elements which are lost to minus figures. Vertebre are created 
under the operation of this law. 
The figures marked A” C’ and D” are rendered equal 
with the figure B” by subtracting the elementary piece 0 
from them. The dotted element 6 is that quantity minus 
which would establish the figures A”C” and D” as the 
homologues of B”. But the element marked 2 in figs. 
A’ B’C’ and D” is still persistent and the same. It is 
the exogenous process of the neural arch being produced 
of the same elementary nucleus with this arch, and there- 
fore cannot be mistaken for that element, which we have 
withdrawn, and which we have marked 6 in those figures. 
The element 0 is autogenous, that is to say it is developed 
from a distinct nucleus. 
The exogenous process 2 fig. A” is therefore contradis- 
tinguished from the autogenous process 0b of the same 
figure. We have abstracted the autogenous element 0 
from the figs. A”C” and D”, and thereby rendered them 
homologous to the fig. B”. In all the figures A” B’C” 
and D” the exogenous transverse process 2 persists, there- 
fore we are always to read 2 of fig. B” the dorsal vertebra 
as identical with the piece 2 seen in all other vertebree, 
and never to confound the piece 2 with the autogenous ele- 
ment 0 of any of those serial vertebree. 
The figures H’E”’ KE” of this plate express the same 
meaning as they did in the former plate. They are atro- 
phied vertebra, or minus certain elemental parts proper to 
the other classes of vertebre. But the elements which 
they contain have still their homologues in the full verte- 
bree elsewhere developed. 
The figures EYE’ F” are proportionals of smaller 
quantity than is proper to the full vertebral form. They 
are the centrums of vertebre, and this name amounts 
to the same thing as if we had said that they were meta- 
morphosed from vertebral forms fully equal to D”C” B” 
or A”. 
When, therefore, we consider all those several figures 
comparatively, we are enabled to come to the plain conclu- 
