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.