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Updated: May 31, 2025
The acoustic nerve is formed from ectodermic cells of the hind brain, and develops from the nervous structure that appears at its dorsal limit. On the other hand, all the membranous, cartilaginous, and osseous coverings of the labyrinth are formed from the mesodermic head-plates.
Now every person must see that the weight of the child's head and shoulders, resting for a considerable time on the slender cartilaginous spinal column, may easily bend it. And a curvature, thus given, may, and often does, deform children for life. Dr.
Whether this explanation be true or not, a glance at a chart, showing the geological succession of occurrence of the different kingdoms, proves that in the oldest palæozoic periods there were well-developed cuttlefish and crabs before there were any vertebrates worthy of the name. If any were present, their skeleton was purely cartilaginous and not preserved.
'But, sir, said Scythrop, 'a key-hole may be so constructed as to act like an acoustic tube, and an acoustic tube, sir, will modify sound in a very remarkable manner. Consider the construction of the ear, and the nature and causes of sound. The external part of the ear is a cartilaginous funnel. 'It wo'n't do, Scythrop. There is a girl concealed in this tower, and find her I will.
It afterwards atrophies; but the relic of the atrophied caudal vertebrae and of the rudimentary muscles that once moved it remains permanently. Sometimes, in fact, the external tail is preserved. Three dorsal vertebrae, from a human embryo, eight weeks old, in lateral longitudinal section. v cartilaginous vertebral body, li inter-vertebral disks, ch chorda.
Its fore-feet are largest, and powerful muscles enable it to dig up the soil and roots which oppose the formation of its galleries, and which are thrown up as they become loosened. The nose, or snout, is furnished with a bone at the end, with which it pierces the earth, and in one genus this bone has twenty-two small, cartilaginous points attached to it, which can be extended into a star.
SHARKS. Of all groups of living fishes the sharks are the oldest and still retain most fully the embryonic characters of their Paleozoic ancestors. Such characters are the cartilaginous skeleton, and the separate gill slits with which the throat wall is pierced and which are arranged in line like the gill openings of the lamprey.
At this time they had diseased and atheromatous arteries, and Chang, who was quite intemperate, had marked spinal curvature, and shortly afterward became hemiplegic. They were both partially blind in their two anterior eyes, possibly from looking outward and obliquely. The point of junction was about the sterno-siphoid angle, a cartilaginous band extending from sternum to sternum.
Philips in the Aymestry limestone, being apparently the first examples of vertebrated animals which breathed upon our planet. In the upper Ludlow rocks, remains of six genera of fish have been for a longer period known; they belong to the order of cartilaginous fishes, an order of mean organization and ferocious habits, of which the shark and sturgeon are living specimens.
The topmost joint is pear-shaped, with a tuft of whitish hair and spines on the apex, out of which the new growth pushes. Cushions large, about 1 in. apart, furnished with a tuft of short, grey hairs and short spines, with a large one at the base. The character of this large spine is exceptional, being broad, flat, cartilaginous, whitish, and curving downwards.
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