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44 THE HARVEIAN ORATION, 1903 sity will not be a satisfactory explanation of the composition of living protoplasm which is ever in a state of flux; the continuous decompositions and reconstructions of which underlie its activi- ties, are indeed phases of its living. Hitherto all attempts to ascertain the composition of the bioplasm have resulted in killing the material, and hence the solution of the question is evaded. And although proteids are obtained from living protoplasm, there is no proof that they exist as such in the living matter, but rather are they the dead derivatives of what is killed in the process of examination.

Theories of the constitution of proteids arrived at by the attempted synthesis of these substances have been provisionally set out, and though no one of them is free from objection, it may reasonably be supposed that consistent with pre- vailing chemical theories, they are on the right lines. Among these should be mentioned that propounded by our distinguished Fellow, Dr. P. W. Latham, according to which what he terms “ living proteid ” is composed of a chain of cyan- alcohols and a thio-alcohol united to a benzene nucleus. These cyan-alcohols are exceedingly unstable and prone to undergo intramolecular changes, properties also possessed in a marked degree by bioplasm, and similar bodies are ob- tained from the disintegration of both cyan-