ASPECTS AND ETIOLOGY OF CARCINOMA 49
very clear why the problem of the nature of cancer should be an embryological one at all. It is a disease carrying with it death and destruction. On the other hand, the problems of the embryologist, as generally understood, treat not of disease, but of the blossoming-forth of life itself—of the phenomena which culminate in the appearance of new living beings. Death and decay would seem to he things of which, from. his researches, the embryologist might be expected to obtain no practical knowledge. He is supposed to be concerned with “ das Werden,” while “das Vergehen” is beyond the scope of his researches. Would that it were so! Unless he shut his eyes to plain facts, “ das Vergehen “ in the midst of “ das Werden “—death in budding life itself—is continually before him.
The conviction impressed upon the writer’s mind from many years devoted to the study of the mode of the development of the higher animals, the vertebrata, is that everywhere and at any point atrophy and death may be met with in any individual life-history. Death and degeneration of cells, of organs, of organisms, of embryos themselves, are among the commonest phenomena under the eyes of the embryologist. His textbooks, even his published researches, may be silent of these; for, as a rule, he believes himself to be concerned solely with the corning-into-being; and the opposite aspect, the decline of life, he leaves severely alone. It is not, in his tacit opinion, a theme of the science of embryology. This view of the problems of the science has for many years failed to commend itself to the writer, and in his own researches he has endeavoured to take account of everything happening and capable of being observed during the developmental cycle, whether progressive or retrogressive.