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The general character of tertiary manifestations may be stated as follows: They attack by preference the tissues derived from the mesoblastic layer of the embryo the cellular tissue, bones, muscles, and viscera. They are often localised to one particular tissue or organ, such, for example, as the subcutaneous cellular tissue, the bones, or the liver, and they are rarely symmetrical.
Again, we have the following from one of the foremost pathologists, as to the strict and rather narrow limits of even pathologic change: "Epithelium and gland cells ... never become converted into bone or cartilage, or vice versa; while, again, it may be laid down that among epiblastic and hypoblastic tissues, on the one hand, and mesoblastic tissues on the other, there is no new development or metaplasia of the most highly specialized tissues from less specialized tissues; a simple epithelium cannot in the vertebrate give rise to more complex glandular tissue, or to nerve cells; in regeneration of epithelium there is no new formation of hair roots or cutaneous glands.
But it also involves him in a belief in the rigidity of chemical reactions; and we are entitled to ask for an explanation of the identical behaviour of the chemical reaction in connection with epiblastic and mesoblastic cells both pure chemical compounds ex hypothesi and, as far as we can tell from their normal behaviour, widely differing from one another.
A most remarkable and interesting experiment; it has this very important limitation that it is always epithelium with which it has to do, whereas in Wolff's experiment the regeneration takes place from mesoblastic tissue. The cause of the transparency may be a chemical reaction it depends a good deal upon our definition of that phrase. Is protoplasm a chemical compound?
His pamphlet, On the Mesoblastic Origin of Excitomotor Nerve Roots, had won him his fellowship of the Royal Society; and his researches, Upon the Nature of Bathybius, with some Remarks upon Lithococci, had been translated into at least three European languages.
"When differentiation has advanced so that such distinct types of tissue have been formed as connective tissue, epithelium, muscle, nerve, these do not again merge through metaplasia. There is no evidence that mesoblastic tissues can be converted into those of the epiblastic or hypoblastic type, or vice versa."
But once or twice lately there had been signs that a third interest was creeping into his life, and he had found his attention wandering from the fate of the mesoblastic somites or the probable meaning of the blastopore, to the thought of the girl with the brown eyes who sat at the table before him. She was a paying student; she descended inconceivable social altitudes to speak to him.
It follows the long axis of the body in the shape of a cylindrical axial rod of elastic but firm composition, equally pointed at both ends. This chordalemma is often called the "inner chorda-sheath," and must not be confused with the real external sheath, the mesoblastic perichorda. Human skull. Skull of a new-born child.
Now the lens is an epiblastic structure, and the iris is mesoblastic. Hence the wonder with which we are filled when we find the iris growing a lens. Loeb attempts to explain this in the first instance by telling us that the cells of the iris cannot grow and develop as long as they are pigmented; that the operation wounds the iris, allows pigment to escape, and thus permits of proliferation.
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