684
SKELETON.
are proper to the plus original. This interpre¬
tation will, I believe, stand the test of rigor¬
ous reasoning, and will teach the anatomist
this, or nothing truthfully besides this, viz.
that if the presential characters of the fore¬
limbs manifest such a diversified condition
as precludes him from naming them quan¬
titatively equal and uniform things, still the
diversity, such as we find it, can have occurred
by no other process or law, save that of de¬
gradation or the metamorphosis of elemental
parts. A certain part is wanting to one
organ compared with another organ ; and if
it be by reason of the want of this part in one
organ, which part is present in another, that I
am unable to name both these organs uniform,
it is no less true that this very want of the
part constitutes the species.
The fore-limbs of the man, the horse, the
ruminant, the carnivore, the rodent, the mar¬
supial animal, the bird, the reptile, are not
quantitatively uniform things, and this is the
only reason why they are various things. If
it be this quantitative difference which in¬
duces us to classify them separately, it is only
this same mode of difference which stands in
our way preventing us from naming them ab¬
solutely alike. The one organ has one part
which the other organ has not, and therefore
both organs are various or special ; but it is
still most true, that it is the want of the known
part rather than the superaddition of an un¬
known part which constitutes both organs
thus special.
The special thing compared with the ideal
unity is simply the minus quantity compared
with the plus quantity. All comparative
method proves this. When I compare the
fore-limb of the ass with the arm of the man,
and endeavour to ascertain the law which has
rendered the first as a form special to the
last, I find that my analysing instrument must
be not the scalpel but the calculation. For
while I see that in the soliped member are
arranged certain parts taking order in the
self-same manner as the like parts in the
human arm ; and while I further discover that
the latter organ developes certain parts,
which parts are not developed for the former,
and that hence only arises the difference or
species ; I must therefore conclude that the
species depends upon the absence of some¬
thing, which thing, being absent, I cannot dis¬
sect by any other instrument than the under¬
standing ; and the thing, though absent, may
be still visible to the mental although in¬
visible to the physical eye.
For the knowledge of the thing absent,
viz. some of the digits of e, fig. 483., is, I con¬
tend, equal to the knowledge derivable from
the actual presence of the very same quan¬
tity, viz. those digits in a ; and, therefore, so
long as I know the quantity which is absent
from one ens to be the same as the quantity
which is present to another ens, this must
furnish me with the idea of equality, or the
uniformity, as salientiy as if the quantity were
present for both enses. When, for example,
I compare the soliped or the cloven foot
with the human hand, I find that the lesser
ens is contained in the greater ens, and that
the other parts, which are wanting to the
lesser, are still manifest in the greater; there¬
fore I conclude, that as the greater, viz. the
human hand, can undergo a metamorphosis
or subtraction of parts, so as to reduce it to
the proportions of the cloven or the soliped
organ successively, so has the original or plus
quantity, which may be regarded as equal to
the human hand, undergone a metamorphosis
of parts in such degree as now yields for our
contemplation the special or minus quantities,
which we name cloven or soliped foot.
Prop. XLI. The scapulary and pelvic mem¬
bers are homologous. — In a former place I
have given reasons why we should consider
the clavicles, the pubic, and ischiadic bones
as the homologues of ribs; and therefore I
shall not need their presence in this place
while holding comparison between the fore
and hind members.*
The fore-limb (fig. 485. a.) separated from
the clavicle, consists, like the hind limb (e),
separated from the pubis and ischium, of a fixed
and invariable number of segments ; and the
parts which constitute these segments in both
are absolutely corresponding. The scapula
(a) corresponds to the ilium (e) ; the hu¬
merus (b) to the femur (f) ; the radius (d)
to the tibia (h) ; the u)na(c) to the fibula (g).
The hand is manifestly the counterpart of the
foot. The carpus represents the tarsus ; the
metacarpus corresponds to the metatarsus :
the phalanges of the hand are represented in
the phalanges of the foot. The pisiform bone
(q) of the carpus is similar to the os calcis (q)
of the tarsus ; the great toe represents the
thumb ; the little toe simulates the little
finger. The common structural identity be¬
tween both organs is plainly manifest at all
points save one ; and this, though often at¬
tempted to be explained, has not as .yet
yielded up its mystery. How happens it
that the patella Qi) and fore aspect of the
hind limb (e), corresponds to the olecranon
(h) and back of the fore-limb (a)? I believe that
the complete solution of this problem may be
had from the following remarks made in
reference to fig. 485.
On comparing the right scapulary organ
(a, b, c, d) with the left pelvic. member
(e, f, g, h), I find that the fore aspect of the
former does not correspond to the fore aspect
of the latter ; but when I compare the back
of the arm a, b*, c*, d* with the front of the
lower member (e, f, g, h), their correspond-
* Yicq d’Azyr regarded the coracoid and acromion
processes of the scapula as representing the pubic
and ischiadic bones, while Cruveilhier states it as
his opinion that the spine and acromion process of
the scapula has no part analogous to them in the
ilium. Professor Owen considers the clavicle as the
homologue of the os pubis, agreeing in this view
with Cruveilhier. But, according to Professor
Owen’s views, it is not with the rib that either the
clavicle os pubis or ischium manifests an homology ;
on the contrary, he regards the iliac bone and the
scapula as the true representatives of the ribs —his
pleurapophysial elements.