THE CANCER PROBLEM 115
On p. 587 he arrives at the important conclusion that the digestion in the frog’s egg (prior to the appearance of an embryo) and in the blastoderm of the chick (with the embryo removed) must be a purely intracellular acid one.* For comparative and other reasons I now apply this conclusion to the trophoblast of a mammal and to the cells of a malignant neoplasm. No more than those of the trophoblast do the cells of a cancer contain yolk. None the less, in both the digestion must be the “ ancestral “ acid “peptic “ (intracellular) one, characteristic of the asexual generation of a vertebrate, for this has been handed down as an unconscious memory from the time when the mammalian yolk-sac contained food material. Recent researches, especially those of Vernon, have revealed the presence of traces of trypsin in many organs of the body. But this enzyme has never been, and cannot be, demonstrated in any malignant tumour. On the contrary, the work of Petry ** on many carcinomata and sarcomata has proved the occurrence in these of a proteolytic ferment. From the author’s account of his
* The antithesis between digestion in an acid and in an alkaline medium struck me, as apparently it did my old friend and teacher, Professor M. M. Hartog. At the present time I do not think that we have got to the bottom of this; but undoubtedly the ferments of cancer act in an acid medium, while those of the sexual generation, man, act best in an alkaline medium—with the exception of pepsin; but the peptic digestion of the stomach, although important in its action upon fibrous tissue, thus loosening such things as muscle-fibres (flesh), can on occasion (after removal of the entire stomach by operation) be dispensed with. For shortness and clearness, when this chapter was first published, I spoke of “acid-ferments” and “alkaline-ferments,” meaning thereby ferments or enzymes acting respectively in acid and alkaline media. A certain anonymous critic might note this, and in future be mindful of the maxim, “Teach not a parent’s mother to extract the embryo juices of the egg by suction,” etc.
** Petry, Eugen: “Em Beitrag zur Chemie maligner Geschwülste,” Zeitschrift fur Physiologische Chemie, 1899, vol. xxvii., p. 398.