TRANSACTIONS OF THE SECTIONS. 93 
preceded by a calcified dm1, and the dmm (deciduous molars) in use‘answer to 
dm2,dm3 and dm4 in the horse and Anoplotherium. The permanent molars of 
2 
sar answering to m1 and m2 in the upper jaw, and to m1, m2 and 
m 3, in the ae jaw of the horse. With regard to the human subject, of which 
the deciduous and permanent teeth were formulised in the author’s ‘ Odontography,’ 
the first dm answers to dm 3 in the dog, horse, &c., and is succeeded in the eighth 
year by a pm, answering to p 3, and dm4 is succeeded by p 4, before the completion 
of the tenth year: m1 usually makes its appearance in the sixth year ; m2 between 
the twelfth and fourteenth years; m3 at or after the eighteenth year, whence it is 
called the ‘ wisdom-tooth.’ 
Now the description of the foregoing anatomical facts by the ordinary language 
and verbal definitions of the teeth would occupy about five pages of type used in 
‘ Bell’s Anatomy,’ and one disadvantage attending such tax upon the efforts of the 
attention and memory was to enfeeble the judgement in forming its conclusions, and 
to impair the power of seizing and appreciating the results of the comparisons. 
Prof. Owen concluded by stating his conviction that nothing would influence 
more the rapid and successful progress of the knowledge of the structure of animal 
bodies than the determination of the nature of the parts by tracing their homologies, 
and the condensation of the propositions respecting them, by attaching to the parts 
so determined of symbols, or at least single substantive names, distinctly defined. 
The bones might -be denoted by. simple numerals, as was proposed in his work on 
the ‘ Archetype of the Skeleton.” And the effect of the few symbols for the teeth, 
which, when explained, were so easily remembered, had been shown to be to render 
unnecessary the endless repetition of the verbal definitions of the parts, to harmonize 
conflicting synonyms, to serve as an universal language, and to convey the writer’s 
_ meaning in the fewest and clearest terms. The entomologist had already partially 
_ applied this principle with much success, and the signs ¢ and 9 for male and female 
constantly occurred: the astronomer had early availed himself of it in the signs © 
_ and ) for the sun and moon, and in the different symbols of the planets, &c.; the 
chemist was greatly advantaged by his extensive system of symbolical notation ; and 
Mr. Babbage had ably advocated the use of this powerful instrument of discovery 
in geometrical science, in his paper ‘On the Influence of Signs in Mathematical 
Reasoning.’ 
; 
the dog are = oa 
On the Value of the Origins of Nerves as a Homological Character. 
By Prof. Owen, M.D., FLRS. 
He stated that he was led to offer a few remarks on this subject from the circeum- 
stance that the supply of nerves.to the arms of man from the lower cervical pairs, 
and not from cranial nerves, had formed a difficulty to some in accepting his deter- 
mination of the general homology of the arms as ‘ diverging appendages of the costal 
arch of the occipital vertebra.’ Since the determination of a general homology was 
dependent on that of the special homology of parts, it was requisite to inquire how 
far the preliminary and minor conclusions were affected by that condition of the 
‘nerves which had been supposed to invalidate the major proposition cited. 
_ The author assumed that it would be granted that the arms of man were homolo- 
us with the fore-limbs of beasts, the wings of birds, and the pectorals of fishes. But 
‘in the wing of the fowl the nerves were derived from the thirteenth and fourteenth 
pairs counting backwards from the brain, whilst the homologous limb in man received 
nerves from the fifth to the eighth pairs. Taking a closer instance of special homology, 
Prof. Owen showed that the wings of the swan derived their nerves from very differ- 
ent pairs from those that supplied the wings of the swift; and he presumed that a 
still greater difference in their relations to the neural axis must have characterized 
& e nerves of the pectoral paddles in the Ichthyosaur and Plesiosaur respectively. 
e difference in the origins of the nerves of homologous parts was also manifested 
in the ventral fins of fishes, which present such great varieties of relative -position 
_ to the head as to afford the ichthyologist his characters of the orders Abdominales, 
~ Thoracici, Jugulares. 
Now, if these differences in the place of origin of nerves do not invalidate the con- 
