Licence: In copyright
Credit: Tumor growth and tissue growth / by Leo Loeb. Source: Wellcome Collection.
Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.
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![1908.] however, an ovum being in this case responsible for the new forma- tion ; but also in this case the experimentally new-formed decidua, as we call this tissue, dies. The latter variety of growth resembles much more closely the real tumor-growth than do the former; but in this case also the cell- proliferation, and even the life of the newly formed cells, cease, when the cause for the proliferation has disappeared. The cause for the development of an artificial decidua is probably two-fold: in the first place, a general chemical condition exists in the body at that period; and, under these predisposing conditions, a local stim- ulus suffices to produce the tumor-like growth. These new forma- tions might be called transitory tumors, because they have a definite life-cycle; they grow for some time, and then they disappear. In real tumors we find a similar but still more marked cell- proliferation; and they do not have such a definite life-cycle. Real tumors do not retrograde usually, and may even grow, more or less, during the lifetime of the bearer. Furthermore, we do not know the cause of their origin, as we do in the case of the transitory tumor. They grow, and we do not know why. If such tumors grow more rapidly, and especially if they grow deep into the sur- rounding tissue, digesting it, if parts penetrate into the blood- or lymph-vessels and are carried away to distant parts of the body, and here start a new growth, a so-called metastasis, then we call the tumor malignant, or a cancer. We distinguish different varieties of cancer, according to the tissue or variety of cells from which these cancers originate. The malignant tumors derived from epithelial surfaces or gland cells, we cafl carcinomata and the malignant tumors derived from the connective-tissue cells, which unite the functionally more highly developed cells, we call sarcomata. But from whatever tissue these malignant tumors are derived, their main characteristics are identical. During the second half of the last century, pathologists studied very carefully the microscopical character of the different tumors; and they determined quite accurately the genesis of these tumors from normal tissues. They observed how cells began to grow down into the adjoining tissues in cancer; they described the general spreading out of the new formation, and the character of the sec-](https://iiif.wellcomecollection.org/image/b22433752_0007.jp2/full/800%2C/0/default.jpg)
