114 THE ENZYME TREATMENT OF CANCER
blastoderm of a bird, all these being in the main homologous structures or asexual generations. What is found to obtain in the one must hold good in the others, for there is but one mode of vertebrate development. In this direction, when dealing with the yolk and merocytes of fish-development and with the mammalian trophoblast in past years, some results had already been obtained ; and in taking up the thread anew one’s thoughts reverted naturally to the chick blastoderm as a readily obtainable material. Then came the recollection that the work had been done already for the chick and frog. In a recent publication Professor M. M. Hartog* writes (p. 587) “ One thing is clear as the result of this all probability henceforward is in favour of the view that in the animal, as in the plant, a cell can only utilize its reserves secondarily and mediately—by the internal secretion of an enzyme.” The author commences his paper by commenting upon the known facts that it has been shown in every case examined that in the utilization of reserves in plants a ferment or enzyme is always present, which in suitable circumstances can effect in vitro the same process—usually of hydrolysis—which the living organism performs. He next proceeds to demonstrate that in the early development of animals, in the cells of the frog’s egg, in which cleavage is ended, hut no embryo yet present, and in the blastoderm of the three or four days’ chick, there is a proteolytic ferment present. Under proper precautions, this in acidulated solution (from 0.3 to 0.7 per cent. hydrochloric acid) gives the biuret reaction showing the presence of peptone. The reaction is absent in neutral or slightly alkaline solution.
* Hartog, M. M.: Some Problems of Reproduction—II.,” Quarterly Journal of Microscopical Science, 1904, vol. xlvii., pp. 583-608.