Cohnheim's theory was that tumors are formed from foci of embryonal tissue which had been non-utilized or left over in the intra-uterine development of the body. Many have not accepted this idea, but have rather considered that in tumors we witness a reversion of tissue to lower or embryonic types.28 Whether we accept either or neither of these propositions, the idea sought to be conveyed is that in all these morbid structures we have a tissue of low or degraded character, springing in most instances from a connective or non-differentiated tissue. This fact is brought out very clearly in many of these intracranial growths. Virchow29 has said that tumors originate in the cells of the connective tissue, although his law has been condemned as not of sufficient breadth, since it seems to ignore the epithelial and myomatous tumors. Dermoid cysts, of which an example is given in the table of spinal tumors,30 are said to illustrate the embryonic function revived—i.e. the tendency of lower tissues to spontaneously differentiate into higher and more complex ones.
28 Article “Pathology” in Brit. Encyc., by C. Creighton.
29 Quoted by Cornil and Ranvier.
30 Page 1107.
The gliomata are among the most common and characteristic tumors of the cerebro-spinal axis, to which system and its prolongation into the retina they are confined. They invariably spring from the neuroglia or connective tissue of the nerve-centres, and reproduce this tissue in an embryonal state. They greatly resemble the brain-substance to naked-eye inspection, but have, histologically, several varieties of structure. These variations depend upon the relations of the cell-elements to the fibres or felted matrix of the neoplasm. In the hard variety the well-packed fibrous tissue preponderates over the cell-elements, and we have a tumor resembling not a little the fibromata (Obernier). The second variety, or soft gliomata, show a marked increase of cells of varied shapes and sizes, with a rich vascular supply which allies these growths to the sarcomata. The elements of gliomata sometimes assume a mucoid character, which allies them, again, to the myxomata.
FIG. 43.
Flat Glioma-cell with its Fibrillar Connections (Osler).