November 30, 1911] 



NATURE 



159 



wujervations made on all the tumours observed or propa- 

 gated in the laboratory during the past eight years, and of 

 the bearing of their relative constancy and variability upon 

 nature of some forms of cancer. 



\11 three papers are intimately interdependent as regards 

 material upon which they are based, and they overlap 



so far as each treats more especially of particular 

 prublems not excluded from consideration in the other two. 

 Thus, as in all previous reports, the effort is made to co- 

 ordinate the features of cancer as it occurs naturally with 

 its behaviour under experimental conditions. 



New facts are brought forward in support of the view 



' a malignant new growth arises from local causes in 



circumscribed area, and that the relation of each 

 malignant new growth to the affected animal is an in- 

 dividual one, parallel to that obtaining between the organs 

 of the body and the organism as a whole. 



Precise evidence is advanced of the existence of hereditary 

 predisposition to the development of spontaneous cancer. 

 It is apparently of the nature of a predisposition of certain 

 tissues to pass into cancerous proliferation, and is not 

 effective by determining an increased suitability of the 

 animals primarily affected for the growth of cancer as tested 

 by transplantation. 



Tumour-cells derived from a single primary growth are 

 shown to be liable during extended propagation to varia- 

 tions such as are met with, either singly or in combina- 

 tion, in other primary growths. It is assumed that this 

 demonstration permits of the inference that corresponding 

 variations occurring in the course of the prolonged prolifera- 



■ ■ of normal cells under the influence of chronic irritation 



be responsible for the development of some forms of 

 er. 

 he relations between benign and malignant new 



■ iwths, and of both to normal tissue, have been studied 

 both histologically and experimentally on an extensive 

 material. Among the large number of tumour-strains that 

 have been propagated by passage from one batch of mice 

 to another for extended periods, there are included several 

 reproducing very closely the features of normal tissue, 

 either as regards its histology or its limited ^ power of 

 growth in any one animal after homologous transplanta- 

 tion. Some tumour-strains, while retaining almost perfect 

 histological differentiation, grow progressively in any one 

 animal ; while others, notwithstanding that they are quite 

 devoid of histological differentiation, possess only a limited 

 power of growth in any one animal. The gaps between the 

 structure of normal tissue and the least differentiated 

 tumours, on the one hand, and between the growth of 

 normal tissue, when transplanted, and that of even the 

 most rapidly proliferating tumours on the other, have been 

 filled in by a continuous series of tumour-strains. Some 

 of these approximate to normal tissue both in respect of 

 structure and of power of growth on transplantation, and 

 experiment has brought out still more clearly the pure 

 arbitrariness of thp conception of a fundamental difference 

 between benign and malignant new growths. 



The demonstration that cancer occurred in practically all 

 races of mankind and throughout the vertebrates even when 

 living in a state of nature, together with the demonstration 

 of the only manner in which cancer can be transferred from 

 one individual to another of the same species, viz. by 

 implanting living cflis, proved that it was not due to h. 

 common causa! parasite. The wide zoological distribution 

 of the disease, down to marine fishes, showed that it was 

 not n recent acquirement such as might be referred to in- 

 fluences dependent on man's particular forms of civilisation. 

 As has been frequently pointed out, the age-incidence of 

 rancpr in man and animals is, in the absence of communica- 

 biiitv. compatible only with the recognition of the intrinsic 

 cellular nature of cancerous proliferation. 



The parallel behaviour of normal and cancer tissue, both 

 as regards the absence of continued growth and the nature 

 of the cytotoxic reactions induced when cancer is trans- 

 ferred from one animal to another of a strange species, 

 proved that cancer had all the properties distintrnishing the 

 normal tissues of one species from those of another species. 



2 In spit^ of brinr poseeswd of a p'^we' of only limited e^owth in any one 

 an-mal, tumour"! can Vie ma-ntained in exfendrd propaeat'on bv snltaVilv I 

 acceleratint; the raoMitv of passage. This has not yet been accomplished in I 

 the case of normal ti«siips. 



NO. 2iq6, VOL. 88] 



The fact that transplantable tumours grow in normal 

 animals as well as they do in spontaneously affected animals 

 is evidence that the latter do not present a soil for the 

 growth of cancer substantially different from that presented 

 by normal animals. When this fact is contrasted with the 

 almost invariable success of reimplanting into the animal a 

 portion of its own spontaneous tumour, and the almost in- 

 variable failure of implantation of any spontaneous tumour 

 into other spontaneously affected animals, the conclusion is 

 arrived at that each tumour is peculiarly and genetically 

 related to the individual in which it arises. 



This conclusion, drawn from studying the growth of 

 tumours under the different conditions just enumerated, is 

 supported by the results of elaborate experiments on in- 

 ducing resistance or immunity to the inoculation of cancer- 

 cells under these different conditions. The features of 

 resistance bearing upon the nature of cancer are briefly as 

 follows. Resistance is induced only by the living cells, 

 either cancerous or normal, of the same species. Under 

 similar conditions the cancerous cells and the normal cells 

 of strange species are both devoid of the power to induce; 

 resistance. An animal's own tumour and its own normal 

 tissue are devoid of this power, and the means which pre- 

 vent the successful inoculation of the tumour of another 

 individual do not prevent the successful inoculation of an 

 animal's own tumour. Tumour-tissue usually induces 

 resistance against itself quite as well as, and, with regard 

 to the phenomenon of spontaneous healing, much more 

 effectively than, any other tumour. Furthermore, animals 

 which have proved resistant to the repeated inoculation of 

 a tumour have subsequently developed spontaneous tumours 

 showing progressive growth. Thus experimental inquiries 

 into the production of growth by inoculation, on the one 

 hand, and its prevention on the other, agree in demon- 

 strating individual relations as obtaining between a tumour 

 and the animal in which it arises. The individuality of 

 tumour-cells will be referred to later. 



The individuality of cancer, both as regards the organism 

 attacked and the tumour, would thus appear to have been 

 placed at last beyond all further doubt. Such a relationship 

 has long been maintained in various forms on the basis of 

 deductions drawn from histological examination of the 

 tissues at the site of the primary lesion and from the nature 

 of dissemination ; but this interpretation of the findings has 

 been as vehemently combated. The combination of the 

 results arrived at by microscopical investigation and experi- 

 mental study appears to complete the demonstration. A 

 long step has thus been taken in defining the direction in 

 which the future investigation of cancer is alone likely to 

 be profitable. 



The conclusions as to the individuality of cancer are sup- 

 ported also by most important new statistical information 

 given in the last report of the Registrar-General. ' The 

 new tabulation of the data for the years 1901-9 for England 

 and Wales has permitted of an analysis being made of the 

 figures recording the increase of deaths attributed to cancer, 

 which brings out the fact that the increase during this 

 period is referable to certain anatomical regions and not to 

 others. For the first time it is fully demonstrated that it is 

 erroneous to make statements of a disquieting nature about 

 the increase of cancer in general. The analysis also shows 

 that the incidence is very unequally distributed arnong the 

 several situations, indeed, that the whole curve of incidence 

 may be different for different organs. A progressive in- 

 crease up to the highest age-periods is characteristic of the 

 face, lip, mouth, bladder, urethra, and breast only. The 

 other organs show a distinct diminution in the highest age- 

 periods ; but it is not yet possible to determine whether this 

 curve indicates a liability rising to a maximum and followed 

 by a fall, or is merely the result of ascribing deaths to 

 other causes in the case of cancer of internal organs in 

 aged people. Sufiicient has been said to indicate how 

 important are the problems which are solved or revealed b\ 

 the improvement in the details given in the national 

 statistics. 



The study of the occurrence of cancer in mankind, and in 

 domesticated animals in widely separated parts of the globe, 

 has shown that the practice of peculiar customs (involving 



* Seventy- Second Annual Report of the Registrar Ctrneral of Births, 

 rteaths, and Marriag'-s in England and Wales (1909). (His Majesty's 

 Stationery OflTice, 1911.) 



