ASPECTS AND ETIOLOGY OF CARCINOMA 61
One reason* is, perhaps, clear. It is that the further growth of a vagrant germ-cell, or of its progeny, to form a cancer takes place at a much later period than that at which its embryological development into a more or less complete embryo should have happened. (The instances of cancer with embryomata, noted by Wilms, do not form exceptions.) Moreover, it must not be forgotten that we are dealing here with pathological conditions, with phenomena which in some glaring way do not conform to the normal. Cancer is, more or less, an attribute of later sexual life or of old age. For this reason one is inclined to suppose that it is not immediately due to the further development of a vagrant germ-cell itself: that this latter first of all divides many times, as it would do if in the germinal nidus, and that it ultimately forms more or less normal forerunners of gametes, öocytes or spermatocytes. These would he in abnormal situations and under abnormal conditions, and, under some stimulus, they would develop as though parthenogenetically, but abnormally, to form a trophoblast.
At the basis, cancer is nothing more, than the production abnormally of an asexual generation within a sexual generation. Elsewhere analogies may be seen. In hermaphroditism we witness the conversion of the forerunners of male eggs (in what are really females) into sperms. In certain ferns, abnormally upon the asexual generation or fern-plant, what the botanists term “apogamy” is met with—i.e., the appearance of a new sporophyte upon the original one; the formation of a sexual generation or gametophyte, and of sexual organs being skipped. It has been urged from a botanical side that comparison between apogamy in certain ferns and carcinoma in a mammal would not be justified, because the former was an abnormal condition. But we are dealing with abnormalities,
* Compare p. 20, et seq. of the Introduction.