3. Cancer is not wholly a result of traumatism; although local injury may have much to do with its development in some particular locality, even as in connection with the late lesions of syphilis.
4. Cancer is not hereditary in any appreciable degree; although some tendency in that direction has been demonstrated in certain strains of mice.
5. Occupation has not any very great influence on the occurrence of cancer; although it is more frequent in some pursuits than in others.
6. Cancer is not altogether a disease of older years; although its occurrence is decidedly influenced by advancing age.
7. It does not especially belong to or affect any particular sex, race, or class of persons.
8. Cancer is not confined to any location or section of the earth, but has been observed in all countries and climates.
But while laboratory and other investigations have not demonstrated any single cause of cancer and have yielded only negative results, they have, by elimination, cleared the way for a study of its cause along other lines, which are bright with promise. They have also established certain facts which confirm the views which from time to time have been briefly expressed by many who were best acquainted with cancer; namely, that, because of its constant recurrence, and from the failure of surgery to check its rising mortality, it must be of a constitutional nature, intimately associated with dietary or nutritional elements, as I have elsewhere shown.[[5]]
The positive results of laboratory investigation are more encouraging:
1. We know now that the local mass, which we call cancer, represents but a deviation from the normal life and action of the ordinary cells of the body. These once normal cells, for some as yet unexplained reason, take on an abnormal or morbid action, with a continued tendency to malignancy which invades and destroys contiguous tissue, and is associated with a progressive anemia which destroys life.
2. Microscopic study has shown that there is a certain change in the polarity of cells about to be cancer-genetic, with an altered relation of the centrosome to the nucleus. These changes have been well attributed to an alteration in the enzyme contained in the cell, which further depends on the nutrition of the cell as influenced by a faulty metabolism of food elements.