CLELAJNT) ON EXES AND TEANSVEBSE PEOCESSES. 181 
lateral processes, and an inferior arch and spine. If we were to 
compare, in the dry skeleton, one of these vertebrae with the first 
caudal vertebra of JVaseus, we should say that the inferior pair of 
lateral processes in the former corresponded with the inferior por¬ 
tions of the lateral processes in the latter. But were we so to judge 
we should make an egregious mistake as to the whole anatomy of 
the part. Bor when the soft parts are before us, w r e see that in 
Menobranchus as in JVaseus the visceral cavity is prolonged further 
back than the first caudal vertebra, but that it lies entirely below 
the inferior caudal spine, whose tip only reaches its upper margin. 
When we reflect that the great vessels embraced by the inferior arch 
are properly internal to the visceral cavity, we see that the explana¬ 
tion of the phenomenon is, that the abdominal laminae, after start¬ 
ing from the vertebral column, have come into contact beyond the 
great vessels, and have again separated to complete their proper 
circle, without, however, the osseous elements being prolonged into 
this latter part. 
In the same way is to be explained the difference of structure in 
the skeletons of the Flounder and Sole ; for while, in the Flounder, the 
inferior arch of the first caudal vertebra is in series with a pair of 
transverse processes on the last trunk vertebra, disposed as in the 
generality of fishes ; in the Sole, it is in series with inferior arches on 
the six last trunk vertebrae terminating in spines similar to itself. 
But these spines do not project at all into the abdominal cavity; 
they are structures lying, as truly as the transverse processes of the 
Flounder, in the abdominal laminae ; only, on account of the flattened 
form of the fish, and the great development of the muscles compared 
with the viscera, the laminae are temporarily united, so as to sepa¬ 
rate the primary circle into a superior division for the great vessels 
and an inferior division for the viscera. A similar disposition of the 
abdominal laminae is found in the Mackerel; but in the Mackerel they 
separate again immediately after coming in contact, and to the tips 
of the arches completed in the line of their subaortic union are 
attached ribs which pass round the visceral portion of the primary 
circle. In the Herring the line of subaortic contact is stretched out 
transversely, and in it are found bridges uniting the transverse pro¬ 
cesses of opposite sides, whose extremities are prolonged some dis¬ 
tance onwards in the visceral part of the circle. 
Besides this arrangement, there also occur adventitious fibrous 
septa stretching across a part of the abdominal cavity, binding down 
the kidneys, or swimming bladder. These are of very secondary im¬ 
portance in the plan of the animal structure. 
Conclusion .—Many points with regard to processes and bones con¬ 
nected with the vertebrae and ribs, and imbedded among the muscles, 
have not been even alluded to in these remarks, but their leading aim 
has been to convince anatomists that the key to the comprehension of 
the skeleton of the trunk is to be found in its double relation to the 
visceral cavity and chorda dorsalis; both being to it centres, yet in 
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