Page:Microscopicial researchers - Theodor Schwann - English Translation - 1947.pdf/245



AFTER I had finished this Treatise, I received the first part of Wagner’s ‘Lehrbuch der Physiologie,’ Leipzig, 1839; which was just then issuing from the press, and which contained (at page 182) an outline of the development of the animal tissues, communicated by Professor Valentin. The author introduces the subject with some historical remarks, in which he represents my researches as giving an essential completeness to the analogies between animal tissues and vegetable cells which had been previously pointed out, more particularly by himself. There are very many ways of drawing a comparison between two objects, and similitudes may be discovered which are opposed to the whole internal construction of the things in which they are observed. Everything, therefore, depends upon the sort of comparison drawn. If Valentin’s historical representation be justified, the idea of a comparison, similar in its kind to that on which my researches are based, must have a previous existence in his earlier investigations. I have endeavoured to analyse the fundamental idea of my investigation in the commencement of the Third Section of this treatise; it was this—that one common principle of development forms the basis of all the elementary particles of organisms. It originated in a comparison being drawn between a cartilage-cell and a vegetable cell, in such sense, that the molecules are united together for the formation of both of them, in accordance with similar laws, since in both instances a nucleolus is first formed; around this