Certain biological aspects in the general pathology of malignant new growths / by J.A. Murray.

  • Murray, J.A.
Date:
1904
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Licence: In copyright

Credit: Certain biological aspects in the general pathology of malignant new growths / by J.A. Murray. 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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    cbromosomes (heterotype), in number half that found in the younger parts. From the position of these heterotj^je mitoses in relation to tlie growing surface of the tumour in which they occur, they must be regarded as a late phenomenon in the life history of the cells, contemporaneous with the histological dilferentiation going on around them. We hare not found evidence of continued proliferation of the immediate descendants of the heterotypical division, and the analogy of animal spermatogenesis suggests that the heterotype initiates a terminal phase in the life history of the caucer cell as in the spermatocyte. From a consideration of these facts the most divergent conclusions have been drawn. Professor Farmer and his colleagues, who first described the occurrence of heterotypical mitoses in malignant new growths, consider that we have here a transformation of somatic tissue into a kind of reproductive, ‘gametoid,’ tissue, which, qvM its gametoid character, is independent and capable of unlimited further growth. This view of the nature of the chanare which marks the distinc- tion between somatic tissues and malignant new growths had already been advanced by Beatson as a result of clinical considerations. Against this view the general objection may be raised that, while it would explain the occurrence of hetero- typical mitoses in malignant new growths, as regards the powers of growth and self-propagation and independence which they manifest it is no explanation at all. In the vertebrates, where malignant new growths have alone been found up till now, we have no evidence that gametes, or the tissue which precedes them, possess powers of growth at all comparable to those seen in cancer. The analogies drawn from the vegetable kingdom all concern the interaction of independent organisms, not of different tissues of the same organism. When, however, the attempt is made to attack this problem by experiment, and artificial propagation of reproductive tissue in animals is tried, the results are in no way different from those obtained with other tissues. The power of in- dependent growth is very limited, and it is found that the power of regeneration of which the testis is capable (along with the thyroid) is confined to the stages before dift’erentiation of gametes has commenced. The power of propagation of malignant new growths is much greater. AVhile only possible within animals of the same species as that furnishing the initial growth, it is found that the cells can establish themselves and produce masses of tissue as large as the primary growth iu successive animals through long periods. While studying the changes which ensue immediately after transplantation in a tumour of the mouse, we observed nuclear changes which presented a close similarity to a conjugation process. Subsequent observations of an extensive material, embracing over 1,000 tumours of all ages, obtained from three difi’erent primary growths, have tended to confirm this interpretation. Thus the same sequence of nuclear changes is again found in later stages, all evidence of its occur- rence being wanting in the interval. These observations harmonise very well with the appearances which this tumour presents as it increases in size. Numerous secondary centres of growth are always found around the periphery of older tumours, and these secondary masses may in time outgrow that which preceded them. At once the suggestion arises that the cells which conjugate are those which have passed through a reducing division, but till the complete cycle has been elucidated the thesis outlined above must remain a working hypothesis. It is in harmony with what we know of malignant growths, and renders secondary assump- tions unnecessary. The relation it bears to the question of the initiation of the cancer cycle may be emphasised by a short reference to another line of inquiry—that, viz., of the age incidence of malignant new growths. The life cycle of all the higher animals commences by a fertilisation process, on which cell-division ensues, and the rate of this cell-division continually diminishes as life proceeds. Its gradual cessation manifests itself in the onset of old age, and along with this diminishing power of proliferation there is an increasing liability to malignant new growths. The hypothesis outlined above is an attempt to account for the entrance of a new growth cycle without doing violence to what we know of the general course of cellular activity. It involves the assumption that the ordinary tissues of the