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Updated: May 4, 2025
Man's ancestors are round coenobia or colonies of Protozoa; they consist of a close association of many homogeneous cells, and thus are individuals of the second order. Their body consists merely of a primitive gut, the wall of which is made up of the two primary germinal layers. The unsegmented chorda develops between the dorsal medullary tube and the ventral gut-tube. Head-gut with gill-clefts.
Since then, the inflammation and sloughing of the part has been attended with a copious suppuration, great loss of substance, extreme debility and emaciation. From this, I am convinced that the ball has shattered and deadened the bone, and now lies impacted in the medullary canal. In fact, there can be no doubt that the wound is incurable, and that amputation is the only resource.
Similar varieties of osteomyelitis are met with that do not, like the acute forms, go on to suppuration or to death of bone, but result in thickening of the bone affected, both on the surface and in the interior, resulting in obliteration of the medullary canal.
In long-standing cases it is common to find extensive obliteration of the medullary canal, and a considerable increase in the girth of the bone. Alexis Thomson, Edin. Med. Journ., 1906. [Illustration: FIG.
The immediate organs of sense consist in like manner of moving fibres enveloped in the medullary substance above mentioned; and are erroneously supposed to be simply an expansion of the nervous medulla, as the retina of the eye, and the rete mucosum of the skin, which are the immediate organs of vision, and of touch.
Certain of the axons have no primitive sheath and others are without a medullary sheath. *Form and Length of Axons.*—Where the axons terminate they usually separate into a number of small divisions, thereby increasing the number of their connections. These collateral branches, by distributing themselves in a manner similar to the main fiber, greatly extend the influence of a single neuron.
It is not absurd to conceive, that the retina may be stimulated into motion, as well as the red and white muscles which form our limbs and vessels; since it consists of fibres, like those, intermixed with its medullary substance.
These observations are not uninteresting, when we recollect that a solution of the upas-poison poured upon the sciatic nerve, or insinuated into the texture of the nerve, produces also a sensible effect on the irritability of the organs by immediate contact with the medullary substance.
They are the only living Vertebrates that have throughout life a chorda dorsalis and a neural string above it; the latter must be regarded as the prolongation of the cerebral ganglion and the equivalent of the medullary tube. Their branchial gut also opens directly outwards by a pair of branchial clefts.
Before leaving this subject, we mention a marvelous operation performed by Billroth on a married woman of twenty-nine, after her sixth pregnancy. This noted operator performed, synchronously, double ovariotomy and resections of portions of the bladder and ileum, for a large medullary carcinomatous growth of the ovary, with surrounding involvement.
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