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nuclear sequences as met with in reproductive tissues. Extensive enumerations of chromosomes in the mouse gave the average number 36, and raised the suspicion that the accepted number given by Sobotta as 24 was in reality too low. This higher number has also been noted by Michaelis. The examination of the ripening divisions of the egg in this animal (Sobotta generously placed his beautiful material at our disposal) showed that the number was in reality 32. Sobotta himself has recently published the results of a re-examination of his material with this result. The error apparently arose in consequence of the small size of some of the elements and the tendency of others to adhere together.

In these circumstances the amphibian tumours presented an unequalled opportunity for an objective control to the results obtained in human and animal material with smaller cells and chromosomes, such as the mouse and trout. Heterotypical mitotic figures could not be found in any of these growths, and their absence finally disposed of the belief that a reducing division was constant or characteristic of cancer. The conclusion is inevitable that the sources of fallacy and equivocal appearances, some of which are described in the following paper, account for the apparent occurrence of heterotypical mitoses in cancer, and that a true homology does not exist with the maturation processes of reproductive cells.

In this connection it is advisable to refer to certain of the observations of Benjamin Moore, Roaf, and Whitley on the effects of acids and alkalies on developing Echinoderm eggs.

Certain peculiarities of the chromosomes met with in the microscopical preparations of these investigators, were regarded by J. E. Salvin-Moore and C. E. Walker as similar to appearances met with in cancer in association with reduction in the number of chromosomes and accelerated cell-division. It is only necessary to compare fig. 18 and fig. 19, reproduced from the paper referred to, and from Boveri's 'Zellen Studien IV.' respectively, to show that the vesicular chromosomes to which so much significance was attached are neither the consequence of altered reaction of the sea-water, nor similar to the heterotypical mitoses of reproductive tissue. They represent the normal process by which the daughter chromosomes reconstitute the daughter nuclei in Echinoderms. The diminution in the number of chromosomes in these experiments is a consequence of multipolar mitosis, and therefore only indirectly of the action of the medium in which the eggs had been placed.

The conclusion we have arrived at is that the gametoid hypothesis is

based on erroneous interpretations of normal and pathological celldivision in no way related to those met with in the maturation of the

FIG. 18.-Late metaphase of mitosis in cell of Echinoderm blastula. Two groups of vesicular chromosomes. From B. Moore, Roaf, & Whitley, Roy. Soc. Proc. 1906. Cf. Fig. 14.

FIG. 19.-Late metaphase of first segmentation spindle of Echinoderm egg
after Boveri, Zellenstudien, IV., 1904.

sexual elements, and we have therefore felt no compunction in finally discarding it as a working hypothesis, or the corollary that certain figures

observed in the nuclei of adjacent cancer-cells represented a fusion of nuclei comparable to fertilization.

The retention of the normal number of chromosomes in mouse tumours after propagation for many years shows that an alteration in the number of chromosomes, however brought about, is not an essential feature of cancerous proliferation. Normal bipolar mitosis is by far the commonest mode of cell-division met with under these conditions, and the various abnormalities encountered can only be regarded as of very subsidiary importance, and in all probability outside of the direct line of the continuous proliferation which occurs. The amount and the energy of this proliferation in tissue elements of apparently normal nuclear constitution is the cardinal phenomenon, and we must look for its elucidation to the application and refinement of those methods of biological analysis which have been revealed by the study of experimental cancer, and which are the foundation upon which many of the later papers in this report are based.

LITERATURE.

EBERTH, C. J.-Ueber multiple Adenome der Froschhaut. Virchow's Archiv, 1868, p. 107.

EHRENREICH, M., & MICHAELIS, L.-Ueber Tumoren bei Hühnern. Zeitschr. für Krebsf. 1906, p. 586.

JABOULAY.-Journal de Médecine et de Chirurgie pratiques, 1908, p. 239.

KOCH, M. Demonstration einiger Geschwülste bei Tieren. Verh. d. deutschen Path. Ges. 1904, p. 136.

Löwenthal, W., & MICHAELIS, L.-Ueber den Krebs der Mäuse. Zeitschr. für Krebsforschung, Bd. 4, Heft. 3, 1906.

LUBARSCH, O.-Ueber einen grossen Nierentumor beim Kaninchen.

für Allg. Path. u. Path. Anat. 1905, p. 342.

Centralblatt

PETTIT, A.-Tumeurs malignes chez des animaux ayant véçu à la ménagerie du Muséum. Bull. Mus. Hist. Naturelle, Paris, 1897, p. 169.

Idem.-Ibid. 1900, p. 31.

Idem & L. VAILLANT.-Lésions stomacales chez un Python de Seba. Ibid. 1902 p. 301.

Idem.-Fibrome observé sur un Megalobatrachus maximus à la ménagerie du Muséum. Ibid. 1902, p. 301.

PICK, L., & POLL, H.-Ueber einige bemerkenswerte Tumorbildungen aus der Tierpathologie. Berliner Klin. Wochenschr. 1903, nos. 23-25.

PICK, L.-Der Schilddrüsenkrebs der Salmoniden. Berliner Klin. Woch. 1905. PLEAN, M.-Bösartiger Kropf (Adenocarcinom der Thyreoidea) bei Salmoniden. Allgem. Fischerei-Zeitung, 1902, p. 117.

Idem.-Ueber Geschwülste bei Kaltblütern. Zeitschr. für Krebsf. 1906, p. 525,

SMALLWOOD, W. M.-Adrenal tumours in the kidney of the Frog. Anatom. Anzeiger,

1905, p. 652.

SOBOTTA, J.-Die Bildung der Richtungskörper bei der Maus. Anatomische Hefte Merkel u. Bonnet, 1907.

STICKER, A.-Transplantables Lymphosarkom des Hundes. Zeitschr. für Krebsforschung, Bd. i. 1904, p. 413.

Trotter, A. M.-Carcinoma of the Liver in the Cow. Journal of Comparative Pathology, 1905.

WELSH, D. A.-Some recent Observations in Cancer and Tumour Growth. Address to Australasian Medical Congress, Sept. 1905, and Edinburgh Med. Journ. 1906.

[For references to papers from the laboratory of Imperial Cancer Research

Fund, see complete Bibliography in Appendix.]

[Reprinted by permission of the Council from the PROCEEDINGS OF THE
ROYAL SOCIETY, B. Vol. 77, 1906.]

ON THE OCCURRENCE OF HETEROTYPICAL
MITOSES IN CANCER.

BY E. F. BASHFORD, M.D., AND J. A. MURRAY, M.B., B.Sc.

[Communicated by J. ROSE BRADFORD, M.D., F.R.S. Received November 2; Read November 23, 1905.]

[FIGURES 1 TO 15.]

THE present paper refers to a communication* made to the Royal Society in January, 1904. In that paper and its expansion †, published later, we emphasised the significance of the zoological distribution of cancer; we discussed the unique features of the processes responsible for the experimental transmission of carcinoma from one animal to another and the limitations to its successful attainment: we also published a series of figures depicting the characters of the nuclei of cancer cells during division, in the malignant new growths of fishes and mammals. We shall give a different explanation of the mitoses we figured in our earlier communications as resembling the heterotypical mitoses of reproductive tissue. We have found that those mitoses may be interpreted as somatic mitoses with longitudinally split chromosomes. Their apparent heterotypical form is thus due to variations in the development of the achromatic figure, the peculiar form. of the chromosomes and their mode of attachment to the spindle.

Our figures of heterotypical mitoses in cancer confirmed the observations of Farmer, Moore and Walker, communicated to the Royal Society at the preceding meeting, but we dissociated ourselves from their conclusions on the diagnostic value and the significance of the phenomenon. The amount of chromatin entering into the equatorial plate of the dividing cells of human cancer had long been known to be subject to diminution (von Hansemann §, 1893), but the presence of

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Roy. Soc. Proc., vol. 73.

First Scientific Report, Cancer Research Fund.

Roy. Soc. Proc., vol. 72.

§ Studien über die Spezificität, den Altruismus und die Anaplasie der Zellen,' Berlin, 1893, etc.

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