obtained no evidence that the liability to carcinoma of the mamma has been enhanced by in-breeding.

Leaving the negative side of the report and turning to its constructive aspects, it may be well to point out at once, that no generalisation attempting a unification of a mass of new and old facts is brought forward. Although our experience is extensive, it is in reality only relatively so, both with reference to the new facts which are being accumulated rapidly by a large number of other investigators, and with reference to the field of inquiry and the new points of attack opened up by the successful application of the experimental method. At the present time it appears unwise to entertain exaggerated opinions of the importance of the working hypotheses which are formulated successively as the work proceeds. No new generalisation is likely to be permanent till the present temporary specialisation in the experimental study of cancer has passed away. Still, the following papers exhibit that harmony and mutual connection which makes them form a whole.

The papers in the report are arranged in sequence as logically as is possible. Starting with more general papers giving the evidence on which the comparative biological and experimental study of cancer is based, there follow others dealing with particular problems, the experimental production of sarcoma, the alternations in the biological qualities of tumour cells, the means whereby their growth may be prevented or modified, the relations of the tumours to the animal, and the constitutional conditions in organisms suffering from cancer.

An introductory chapter deals with matters of general interest on the incidence of cancer, and its association with very different forms of chronic irritation in mankind. Dr. Seligmann contributes an account of his observations on the occurrence of new growths in British New Guinea, the natives of which are, as he puts it, “but just emerging from the stone-age."

The zoological distribution of cancer is reviewed and new observations are recorded by Dr. Murray: to that account is appended a paper

showing some of the fallacies which account for the apparent occurrence in cancer, of forms of cell division characteristic of reproductive tissues during the ripening of the sexual elements.

After these papers of general interest, the report is concerned principally with the study of cancer in small laboratory animals. The features of spontaneous cancer in mice are dealt with by Dr. Murray on the basis of a very extensive and varied material, the study of which has occupied him for four years. In the course of this paper, Dr. Murray demonstrates the baseless nature of the assertion that surgical interference causes a tumour to become more malignant or necessarily to disseminate. At the same time he breaks new ground in studies on the relations between an organism and the malignant new growth it supports.

Special groups of tumours are described in greater detail in the papers of Dr. Gierke on the hæmorrhagic mammary carcinomata of mice, of Dr. Haaland on the experimental production of sarcomata, and of Dr. Murray on a transplantable squamous-celled carcinoma.

In these papers attention is drawn to important mutations of histological structure in malignant epithelial new growths, which throw light upon the subsidiary importance of histological minutia in the study of malignant new growths of man. These papers illustrate how the experimental method allows us to follow the life history and biological behaviour of a tumour over prolonged periods of time, with the result that the study of cancer has been unburdened of much needless histological lumber. The study of cancer in man had become purely histological, and histological studies in turn had become mere necrology-notes of deaths from tumours of this or that histological order.

Dr. Gierke records observations of importance in reference to the dissemination of cancer once a tumour is present, confirming observations we made in 1904, and adding new facts.

Mr. W. H. Bowen describes experiments on surgical interference with transplanted carcinomata and sarcomata, particularly interference with the blood supply, and records results bearing on the malignant nature of carcinoma and sarcoma in mice, as well as upon the surgical treatment of cancer in the human subject.

Dr. Haaland has made a most valuable contribution to the definition of the circumstances which determine the experimental development of sarcomata during the propagation of carcinomata. The process has occurred nine times in one of our tumour-strains and has been followed step by step. It is recorded with an exactness and detail which have not yet been attempted, and throws much new light upon the mediate relation of the irritation connected with transplantation into new animals, to the onset of a malignant new growth. Observations on this material enable us to substitute an objective study of the inception. of cancer for the abstract speculations which have held the field for so long. The experimental study of cancer in animals has come to have a direct bearing on one of the most conspicuous aspects of the ætiology of the disease in man, as referred to above in alluding to the world-wide association of cancer with very varied irritants having nothing in common beyond this association.

The remaining papers deal mainly with the biology of the tumours of mice, the natural features of their growth, and the experimental means by which it can be modified or inhibited. The papers on the experimental analysis of growth and on the propagation of cancer, discuss alternations in the rate of proliferation of the cells of malignant new growths. These alternations have appeared in their true perspective, only as a result of experimental transference. It is made more certain that the biological qualities of cancer-cells vary in a way that finds expression in an alternation between positive and negative phases of growth. In clinical language these phases are fluctuations in malignancy, and a diminution in the size of a tumour will in all probability be followed by renewed increase. They give indications that

surgical removal should be attempted even though a tumour shows signs of diminished growth, and they help towards a better comprehension of the reasons for the unexpected disappearance of tumours after partial operation, or even when they have been held to be inoperable. In the negative phase of growth the cancer-cell is more vulnerable to those modifications which are induced in the living animal as the result of the absorption of normal or cancerous tissue referred to below.

The paper on the natural and induced resistance of mice to the growth of cancer marks the important advance which was made by the discovery announced from the laboratory in July 1906, that animals could be rendered resistant to cancerous inoculations by preliminary treatment with normal tissue. The relation between normal and cancerous tissue thus established by accurate bio-chemical methods, and carried further, in other papers, by observations on the metabolism of sound animals as compared with others bearing tumours, suggests an historical digression.

At the end of the eighteenth and the beginning of the nineteenth centuries, English investigators were striving to elucidate the nature of cancer by anatomical studies on the relations between cancerous and bealthy tissues. Percival Pott, Jacob, Abernethy, James Wardrop, John Hunter, Astley Cooper, Carswell, Walshe, Everard Howe, Hodgkin and others were closely associated with the endeavour to segregate separate types of cancer, e. g., chimney-sweeps' cancer, rodent ulcer, fungus hæmatodes, and what we now know as lymph-adenoma. The many resemblances of cancerous to healthy tissues received emphasis from some of them. This relation was fully recognised in Germany by Johannes Müller and his pupil Virchow, and, in England by Sir Samuel Wilks. In 1868 Sir Samuel Wilks who published his first paper in which he makes reference to cancer in 1846, indicated how this similarity differentiated the disease from infections. It has been my privilege to enjoy much intercourse with Sir Samuel Wilks, and through his keen interest in the progress of these investigations, modern experimental study is linked up with the results distinguished English

investigators foreshadowed a century ago. It has taken one hundred years to advance from the exact anatomical to the precise bio-chemical study of cancer as recorded in this report.

Dr. Russell has investigated the difference between the processes at the site of inoculation in normal and in resistant animals respectively, and shows that absence of growth in the latter is due to the failure of the resistant animal to furnish a new connective-tissue and vascular scaffolding for the introduced cancer-cells.

In the paper on resistance and susceptibility to transplanted cancer, these investigations are carried a step further. By accurate quantitative methods the delicate gradations of specific resistance are revealed and the results recorded in easily intelligible graphic form, showing, e. g., that the protection which normal tissues induce is most effective against cancers arising from them, for example, skin protects best against skin cancer.

The remaining three papers deal in different ways with the relation of a malignant new growth to its host, viz., with the processes of cancer metabolism. In an earlier paper this subject is opened by Dr. Murray's account of the variations in body weight in spontaneously affected mice, and the results of operative removal and re-inoculation with transplantable carcinoma. Dr. S. Monckton Copeman, and Dr. J. Wilson Hake show, that the rapid building up of cancerous tissue calls forth a compensatory response on the part of the digestive system of the host animal. This has been measured by estimating the amount of HCl secreted by the stomach during digestion. Their results were in the first instance obtained on mice with transplanted tumours. They have controlled and confirmed them by corresponding investigations of the stomachs of normal mice and of mice spontaneously affected with cancer, and by investigating test-meals from human patients. It is hoped that the results of this comparative investigation may contribute materially to a settlement of a much disputed clinical question. At the same time they offer another demonstration of the parallel obtaining