90 Anniversary Address by Lord Rayleigh. [Nov. 30, 



Medallists, 1906. 



The Copley Medal is awarded to Professor Elias Metchnikoff, For. 

 Mem. E.S., on the ground of his distinguished services to zoology and 

 to pathology, particularly for his observations on the development of 

 Invertebrates and on phagocytosis and immunity. From 1866 to 1882 

 Professor Metchnikoffs work was exclusively zoological, and mainly during 

 that period he produced a series of brilliant memoirs dealing with the early 

 development and metamorphoses of Invertebrates. 



Although his name stands in the first rank of investigators of these 

 subjects, the most celebrated of his discoveries are those relating to the 

 important part played by wandering mesoderm cells and white blood- 

 corpuscles in the atrophy of larval organs, and in the defence of the organism 

 against infection by Bacteria and Protozoa. It was on these researches 

 that he based his well-known ' Phagocyte Theory.' Metchnikoff's funda- 

 mental observations were made in Messina in 1882, and were published in 

 the following year. In these he showed that the absorption and dis- 

 appearance of the embryonic organs of Echinoderms were effected by 

 wandering mesoderm cells, which devoured and digested the structures 

 which had served their purpose and become effete. The observation that 

 white blood-cells accumulate in an inflamed area after infection by Bacteria 

 suggested that these cells might also devour and thus destroy the invading 

 microbes, and that the process of inflammation was really a physiological 

 and protective reaction of the organism against infection. The study of 

 the infection of Daphnia by Monospora bicuspidata entirely justified this 

 prediction. The account of the phenomena of infection as seen in this 

 transparent Crustacean was published in ' Yirchow's Archiv ' (vol. 96) in 

 1884, while, later in the same year, Metchnikoff published another paper 

 extending these observations to Vertebrates, and showing the universal 

 applicability of his generalisation as to the essential character of the 

 inflammatory process. 



During the twenty years which have elapsed since the publication of the 

 ' Phagocyte Theory,' Metchnikoff, with the assistance of a host of pupils 

 and disciples from all parts of the world, has been continuously engaged in 

 the study of the reaction of the organism against infection, and in investi- 

 gating the essential features of immunity in the light of the illuminating 

 generalisation laid down in 1884. 



Though of limited range, and therefore inferior in scientific importance 

 to the more fundamental researches carried out by him previously, 



