468 



NATURE 



[March 20, 1902 



are termed " sarcomata," a term as meaningless as its 

 congener, carcinoma. We have, then, speaking roughly, 

 two great classes of tumours, the so-called innocent 

 tumours, or those which grow slowly and locally, and 

 the malignant tumours, which grow rapidly and liccome 

 disseminated all over the body. This latter group, 

 although consisting of two classes, the carcinomata and 

 sarcomata, are generally designated "cancers," and are, 

 no doubt, although, so far as we can ascertain, no specific 

 information is to hand upon the subject, to be the objects 

 of the proposed research. 



As very often happens when facts of unmistak- 

 able significance are wanting, theories are abundant. 

 This is certainly true of cancer. It must at once be 

 admitted of the theories with regard to the causation of 

 cancer, that although they have no doubt been of great 

 value in assisting what may be termed the crystallisation 

 of histological results, they have, tending as they do 

 rather to express one enigma in terms of another, been 

 of little value from the absolute practical standpoint. 

 Six distinct theories have been put forward concerning 

 the pathogenesis of cancerous growths. Perhaps one of 

 the most generally accepted is Prof. \"irchow's theory 

 that these growths are caused by injury or chronic 

 mechanical irritation. There can be no doubt that 

 cancerous growths very frequently affect the parts of the 

 body, either external or internal, which are most 

 frequently subjected to some kind of irritation. Cancer 

 of the tongue in clay-pipe smokers or in the subjects of 

 rough and uneven teeth, cancer of the scrotum in 

 chimney sweeps, due to chronic irritation of the part 

 by soot, &c,, cancer of the breast, of the arms in paraffin 

 and tar workers, of the two ends of the stomach, 

 especially apparent in individuals who masticate im- 

 perfectly, can all be cited as showing the predilection of 

 cancerous growths to parts of the body exposed to 

 constant or intermittent irritation. Perhaps of all the 

 numerous common factors in cases of cancer, chronic 

 irritation is the most constant. It cannot, hovve\er, be 

 regarded as a universal or even adequate explanation of 

 the disease, for, as Cohnheim has pointed out, in 86 per 

 cent, of all the cases irritation apparently plays no part. 

 Prof Cohnheim regards cancerous growths as being due 

 to the abnormal proliferation of embryonic remnants. 

 He assumes that in the development of the individual 

 from the embryo, more cells are produced than are re- 

 quired for the building up of the organ concerned. There 

 thus remains an embryonic cellular remnant. These 

 embryonic cells remain always possessed of one 

 characteristic of this variety of cell, viz. an unlimited 

 capacity for proliferation. These remnants may remain 

 quiescent, and then nothing more is heard of them ; 

 they may, however, under the influence of certain con- 

 ditions, assume active growth, and may thus constitute 

 malignant tumours. There can be no doubt that this 

 theory explains many of the features of cancerous 

 growths, and is greatly supported by the fact that, 

 speaking generally, new growths are prone to occur in 

 parts of the body which are the seats of complicated 

 embryonic development. We have, however, some 

 actual knowledge of embryonic remnants in the so called 

 epithelial pearls which are fairly frequently found in the 

 tonsils, and it must be admitted that these organs are 

 rarely the seats of malignant growths. Further, in 

 Cohnheim's theory the actual cause which stimulates 

 the growth of the embryonic remnant is not defined 

 except in the most general terms, viz. as a condition of 

 n.alnutrition of the surrounding tissue. 



The obvious similarity between malignant growths 

 and the so-called infective granulomata has led many 

 observers to the view that the former disease must, like 

 the latter, have a parasitic origin. The analogy between 

 . these two classes of affection is perhaps the greatest 

 when we take tuberculosis as the type of the infective 



NO. l6go, VOL. 65] 



malady. Tuberculosis at first local, confined, for 

 instance, to a given part of one organ, produces 

 secondary infection in the adjacent lymphatic glands by 

 means of the lymphatics, and subsequently from these 

 tuljercular material may gain entrance into the general 

 circulation, and being carried by it hither and thither 

 may become implanted in the most remotely situated 

 organs and produce tuljerculosis of them. In the case 

 of cancer there is, too, always a primary focus which is 

 strictly local, and in this case also the lymphatic vessels 

 carry the carcinomatous material to the adjacent glands 

 and from them either by means of the general lymphatic 

 system or the general circulation, carcinoma of remote 

 organs may ensue. When we come, however, to 

 examine this analogy, we find that it is more apparent 

 than real. Tuberculosis can readily be conveyed from 

 animal to animal ; this certainly is not the case with 

 cancer. It is true that examples of what may be 

 termed the auto-inoculation of cancer in man are not 

 uncommon ; for instance, in the case of adjacent parts of 

 the body, cancer of the one may spread to the other ; 

 this probably simply means that the cancirous tissue of 

 the one organ becomes ingrafted upon the other. This 

 condition is often referred to as "contact cancer." 

 Ebert has collected twenty-three such cases. The actual 

 infectivity of cancer, using this term in the ordinary 

 sense, is at present doubtful, although several instances 

 are recorded of what may perhaps best be expressed by 

 the French term, " cancer a deux." Nineteen such cases 

 are given by Behia ; in most instances the persons 

 affected were man and wife. Some instances are also 

 on record of surgeons inoculating themselves accidentally 

 with cancer from the cancers of patients upon whom 

 they were operating. 



The similarity between malignant disease and tuber- 

 culosis has led numerous investigators to seek for an 

 organism which would bear the same causative relation 

 to cancer as the tubercle bacillus does to tuberculosis. 

 Carcinomata have received more attention at the hands 

 of these investigators than sarcomata. Into the details 

 of these most interesting researches the space at our 

 command forbids us to enter. The main point of 

 difference between the adherents of the parasitic theory 

 of the origin of cancer and their opponents centres 

 upon the significance of certain undoubted microscopic 

 appearances, chiefly of the growing portions, of cancerous 

 growths. Some observers maintain that these micro- 

 scopical appearances represent an organism of a proto- 

 zoic type, others regard them as due to degeneration of 

 the cancer cells. The majority, however, of micro- 

 scopists do not regard the presence of a parasite in 

 cancerous growths as proved. In the case of sarcomata, 

 the parasite is supv)Osed to be, not of animal, but of 

 vegetable origin, probably a torula. 



If we turn from the study of the hypothetical cancer 

 parasite to a consideration of the influence of general 

 climatic conditions upon the incidence of cancer, we 

 shall be treading upon more certain ground. The 

 existence of so-called "cancer houses ' seems to rest 

 upon very strong evidence. In one instance, six persons 

 within twenty-six years died of cancer in two houses 

 that were under one roof and had a common drainage 

 and water-supply. The inhabitants affected were for the 

 most part unrelated to each other. So intimate appears 

 to be the connection between the existence of cancerous 

 disease and locality that so-called "cancer fields'' have 

 been described. These are found in " sheltered and 

 low-lying vales traversed by fully formed and seasonably 

 flooded rivers and composed of the more recent argil- 

 laceous formations." Districts, on the other hand, 

 which possess the lowest cancer death rate are generally 

 more or less elevated areas composed of the oldest rocks, 

 especially limestone. The difi'erence between the death 

 rates from cancer in different regions in north Germany 



