Elias Mecznikow. 



Ivii 



eytes, to the knowledge and theoretical understanding of which a great 

 number of highly gifted leaders of experimental inquiry — to name only 

 Ehrlich. Behring, and Almroth Wright — have contributed in the most 

 important way. A large series of investigations and records of experiment 

 was now continuously produced by Metchnikoff or by his assistants under 

 his immediate supervision. The ' Annales de lTnstitut Pasteur ' are largely 

 made up of these records and discussions. In 1901, Metchnikoff produced 

 his great book on ' Immunity in Infectious Diseases,' an English translation 

 of which was at once published. The subject branched out into various 

 lines, such as are indicated by the names serotherapy, toxins and anti-toxins, 

 haemolysis, opsonins, and bacteriotropins. It must suffice here to state that 

 Metchnikoff successfully established the doctrine that it is to the healthy 

 activity of our phagocytes that we have to look not only for temporary 

 protection, but for immunity against the micro-organisms of disease. 



Since 1901 — until he fell ill last winter — Metchnikoff was incessantly 

 active in his laboratory, working there from early morning until evening, 

 when he took train to his country house on the heights above the Seine. 

 Earely would he tear himself away from his absorbing work to enjoy a 

 holiday. He went a few years ago to Astrachan, on the Caspian, to enquire 

 for the Russian Government into the occurrence of bubonic plague in that 

 region, and studied also the incidence of tuberculosis in the town populations 

 and among the Kalmuck Tartars. On the latter subject he gave (in response 

 to my urgent request) a valuable lecture in London before the National 

 Health Society (in 1912), and on other occasions he made short visits to this 

 country in order to receive honours and deliver special discourses — as at the 

 Darwin Celebration at Cambridge in 1909. The variety of infective diseases 

 to the experimental investigation of which he turned the resources of his 

 laboratory and his theoretical conceptions is truly astonishing. As late as 

 1911 he wrote : " Perhaps before long it will be possible to explain diabetes, 

 gout, and rheumatism by the injurious activity of some variety of microbe " 

 (preface to the excellent volume, ' Microbes and Toxins,' by Dr. Etienne 

 Burnet, published in London by Heinemann). 



In 1903 he found time to write a profoundly interesting popular book, 

 ' The Nature of Man ' (London : Heinemann), in which, among other things, 

 he discourses of old age, and his view that unhealthy fermentation commonly 

 occurring in the large intestine produces poisons which are absorbed, and 

 lead to deterioration of the tissues of the walls of the arteries, and so to 

 senile changes and unduly early death. He satisfied himself, experimentally 

 and clinically, that the use of " sour milk " as an article of diet checks or 

 altogether arrests this unhealthy fermentation in the intestine by planting 

 there the lactic bacillus, which, forming lactic acid, renders the life and 

 growth of the bacteria of those special poisonous fermentations (which 

 cannot flourish in an acid environment) impossible. Hence, he himself daily 

 took a pint or so of sour milk, and he recommended it to others, and 

 arranged for the commercial preparation of a particularly pure and agreeable 



