— 
, ey ee ae ee 
i 
pet er eS 
ON THE VERTEBRATE SKELETON. 219 
anterior and antero-lateral walls of the cranium, defends the rhinencephala 
and transmits the olfactory nerves, but is altogether distinct from and pos- 
terior to the capsules of the organs on which those nerves are ramified. 
In the crocodile Cuvier restricts the term ethmoid to the cartilaginous 
lamine, capsules, or supports of the olfactory ramifications after the nerves 
have left the cranium. In mammals the ethmoid is made to include both the 
bones that close the cranium anteriorly, support the rhinencephala, give exit 
to the olfactory nerves, and those which defend and sustain the enormously 
developed. and complex superior parts of the organ of smell*. Whilst this 
confusion is permitted to vitiate osteology, it is plain that no intelligible 
homological or other proposition can be predicated of the ‘ ethmoid.’ 
When Cuvier, with.reference to the hypothetical possibility of the homo- 
logue of the frontal forming part of the bone 7—11 in the frog, adverts to 
the second chance of bringing the ‘cs en ceinture’ into the ordinary cate- 
gory of cranial bones, by viewing it as the ‘ethmoide,’ he adds, that it would 
then be “un ethmoide ossifié, ce que sera une grande singularité” (2. 
p- 388). Here it is obvious that the predominating idea of the ethmoid was 
that presented to his mind by the capsules of the olfactory organ in the 
crocodile“and other reptiles,;which he had so called, and which are wholly or 
in great part cartilaginous. But the parts of Cuvier’s ethmoid in birds and 
mammals, which are in functional and physical relation with the cranial cavity, 
thinencephala and olfactory nerves, are ossified : the bone, also, to which he 
gives the name ‘ ethmoid’ in fishes (fig. 5, 15) is ossified ; and, what is more 
to the purpose, the bones (11) in fishes, ophidians, chelonians and saurians, 
which repeat the essential characters of the batrachian ‘ os en ceinture, are 
likewise ossified. 
General homology teaches that the bone or bones in relation to the defence 
of the rhinencephala and the transmission of their nerves belong to one class, 
and that the parts of the skeleton, whether membranous, gristly or bony, 
which form the capsule or sustain the olfactory organ itself, belong to another 
and very different class of parts of the skeleton. But, not to anticipate what 
belongs more properly to a subsequent section of this report, observation 
shows the two parts to be physically distinct in all vertebrates except mam- 
mals, and to be distinct in the foetus of these. Whether we restrict the term 
*ethinoid’ to the neurapophysis or to the sense-capsule (which in mammals 
constitutes the ‘ conchz superiores’ and cells of the ethmoid), the term must 
be applied arbitrarily in its extended or homological signification, since the 
neurapophysis dismisses the nerve by a single foramen or groove in all the 
vertebrates below mammals. The multiplied foramina in the neurapophysial 
or cranial part of the anthropotomical ‘ ethmoid,’ whence that name, as well 
as the special designation of the part called ‘lamina cribrosa,’ are modifica- 
tions peculiar to the mammalian class, but not constant here, and they form 
no essential homological character of the bone in question. It appears to 
me preferable, since we have two essentially distinct parts of the skeleton 
combined in the mammalian and human ethmoid, to restrict the term to the 
* Objecting to Oken’s idea, that the prefrontal in the crocodile was homologous with the 
part of the ethmoid called ‘os planum’ in anthropotomy, Cuvier says, “ Or l’os planum ne 
parott jamais sur la joue; il ne se montre plus dans J’orbite 4 compter des makis si ce n’est 
un petit point dans les galeopitheques et dans quelques chats. Dans tous les autres mam- 
miféres l’ethmoide est entiérement enveloppé et caché par le palatin’”’ (note that significant 
connection) “et par le frontal et spécialement par cette partie du frontal dont il est main- 
tenant question et qui se détache dans les ovipares. Le véritable ethmoide est enveloppé 
de la méme maniére dans le crocodile, quoique presque toutes ces parties restent cartilagi- 
neuses.”—Ossem. Foss., v. pt. i. p. 73. i 
Q 
