(2) The lining of the tube passing through the body; its backwaters, out-growths and appendages.
It is these two layers which, as Mr Wright so aptly remarks, are in direct contact with the outer world. Now, while the carcinomata (which constitute the class of cancers chiefly discussed in this book) in general affect people who have passed the midpoint of life—those for whom, as Rabelais says, it is midi passé—the sarcomata, which are less common than the carcinomata, are rather more frequently, yet not exclusively, found in young people; in those indeed, who have not reached life’s apogee. It is important that these facts should be borne in mind, for generalisations founded upon the study of carcinomata alone cannot be necessarily true in respect of all Cancer, unless the use of the term cancer be restricted to the class technically known as carcinoma. To say that Cancer can be prevented if constipation is avoided is clearly misleading, when we remember that quite young children, nay, infants, may be the subject of sarcoma; unless of course we define cancer, as some would do, as the kind of growth that, ex hypothesi, is prevented when constipation is avoided. It is confusion of this sort, bred by slovenly expression out of loose thinking, that is in great part responsible for the present bewilderment of the public.
Another fertile source of confusion is the obscurity that attends both the popular and the professional use of the words “cause”, “causation”, and the like. The public demands that “the” cause of cancer be discovered, and is prepared to pay generously that this discovery be made. Unfortunately neither the public, nor men of science, care overmuch to discuss what they mean by cause and causation. This is no place in which to trench upon a province unsuccessfully explored by Locke, by Hume, and by Kant. Yet it is of vital importance that all doctors, scientists, and laymen should recognise two different uses of these words.
When we speak about “the” cause of a “disease”, in a generalised or conceptual sense, as when we say that Koch’s bacillus is “the cause of tuberculosis”, we are really defining our concept of the disease in terms of one correlative. We are saying that tuberculosis is a disease in which Koch’s bacillus is invariably present. A circulus in definiendo is only just escaped because we happen to know that, if Koch’s bacillus is injected into certain animals, the “disease” as we say, develops. Koch’s bacillus is the one constant correlative found in all cases of the kind that we agree to call tuberculous, by reason of certain clinical and pathological signs that we find. Possibly even this statement is not to be taken as absolutely true; though it represents what we find it convenient to say. But, when we thus declare Koch’s bacillus to be “the” cause of tuberculosis, we have by no means exhausted the study of all the correlations that may be called causal in respect of particular cases. Of ten cases of tuberculosis, each one exhibiting Koch’s bacillus, we may say that for each particular case “the” cause of the illness is different.
Thus:
A. is tuberculous because he was gassed in France;
B. is tuberculous because he was infected by his sick wife;
C. is tuberculous because he drank tuberculous milk;
D. is tuberculous because he worked in an ill-ventilated factory;
E. because he was exposed to wet and cold; and