ASPECTS AND ETIOLOGY OF CARCINOMA 63
was apparently a despairing one when enunciated, but only “apparently,” for cancer had still to reckon with some of the “brigades” and “divisions.”
As conceived here, carcinoma would be a disease peculiar to mammals; for, as recognized by the writer years ago, in them the asexual generation has become parasitic in adaptation to uterine development. The possibility of carcinomatous development postulates uterine gestation—at least, for the normal life-span of the asexual generation; i.e., until what was termed the critical period. In fishes, such as the skate or dog-fish, neither a vagrant germ-cell nor its progeny could develop into a carcinoma, for the asexual portion of the life-cycle is not passed as a parasite upon the parent (even in forms with an apparent uterine development), but in seawater: in other words, below the marsupial and higher mammals the asexual generation is not adapted for a parasitic existence upon the parent organism, and thus cannot easily abnormally become a parasite upon it. Carcinoma is not known below the mammals ;* the animal lowest in the scale in which it has been recorded being the short-headed phalanger (Belideus breviceps).** The disease is a corollary to uterine gestation.
If the cycle of development of the higher animals really be that concluded by the writer, if his interpretation of the phenomena of mammalian development—which are not in the least based upon facts or factors noted in cancer, but upon normal development here—if these be correct, the nature of carcinoma is not hypothetical at all, but is actually known. More than one font cannot be assumed, and if one fountain-head be shown, all other
* See, however, the closing lines of this chapter.
** Bland-Sutton, J.: “Evolution and Disease,” London, 1890, p. 247, Fig. 123. The case is one of cancer in the marsupial pouch.