i64 



NATURE 



[February 9, 1922 



he met Madame Metchnikoff, who was then a 

 schoolgirl. Finding that she was interested in 

 zoology, he undertook to teach her, and shortly 

 after they married. His second marriage was a 

 happy one; his wife, although more directly in- 

 terested in art than in science, became a willing 

 disciple. Madame Metchnikoff thus describes their 

 work together : — 



" It was both delightful and profitable to work 

 with him, for he opened out his ideas unreservedly 

 and made one share his enthusiasm and his interest 

 in investigations ; he could create an atmosphere of 

 intimate union in the search for truth which allowed 

 the humblest worker to feel himself a collaborator 

 in an exalted task." 



Metchnikoff appears to have exerted a great influ- 

 ence in the university, especially upon the young 

 men, but was regarded with some suspicion by the 

 authorities, owing to the independence of his ideas 

 and the directness with which they were expressed. 

 After the assassination of Alexander II. in 1881 

 the government of the university became more and 

 more reactionary, and the independence of the uni- 

 versity was threatened. Though not greatly inter- 

 ested in politics, Metchnikoff' seems to have become 

 unavoidably involved in these quarrels, and ulti- 

 mately, finding the conditions intolerable, resigned. 



His resignation of the Odessa chair and the cir- 

 cumstances which led to it preyed upon his mind. 

 Another period of ill-health ensued associated with 

 intense depression, during which suicide was again 

 attempted. In order not to harrow his family by 

 a suicide that was too obvious, and at the same 

 time to put the occasion to the use of ascertaining 

 whether relapsing fever could be transmitted by 

 inoculation, he injected into himself some blood 

 from a patient suffering from that disease. He had 

 a prolonged attack of the fever, but this shock treat- 

 ment cured his pessimism, and after his recovery he 

 had a renascence of vital energy such as he had 

 not enjoyed for years. Moreover, thanks to the 

 inheritance of landed property, the Metchnikoffs 

 were now in a position of modest independence and 

 able to live where they liked. Accordingly in 1882 

 they repaired to Messina to take advantage of the 

 opportunities for study afforded by the sea fauna 

 of the Mediterranean. 



It was at Messina, at Christmas of that year, 

 that what Metchnikoff regarded as the great event 

 of his scientific life occurred. It is described by 

 him in his own words as follows : — 



" One day, when the whole family had gone to 

 a circus, I remained alone with my microscope, 

 observing the life in the mobile cells of a trans- 

 parent starfish larva, when a new thought suddenly 

 flashed across my brain. It struck me that similar 

 cells might serve in the defence of ihe organism 

 against intrudeis. I felt so excited that I began 

 NO. 2728, VOL. 109] 



striding up and down the room, and even went to 

 the seashore to collect my thoughts. 



"I said to myself that, if my supposition was 

 true, a splinter introduced into the body of a star- 

 fish larva, devoid of blood-vessels 01 of a nervous 

 system, should soon be surrounded by mobile cells, 

 as is to be observed in a man who runs a splinter 

 into his finger. This was no sooner said than done. 



" I fetched some rose-thorns and introduced 

 them under the skin of some beautiful starfish larvae 

 as transparent as water. 



" I was too excited to sleep that night in the 

 expectation of the result of my experiment, and 

 very early the next morning I ascertained that it 

 had fully succeeded. 



" That experiment formed the basis of the phago- 

 cyte theory, to the development of which I devoted 

 the next twenty-five years of my life. 



" A zoologist until then, I suddenly became a 

 pathologist." 



It appears that the discovery of phagocytosis first 

 disclosed to him the possibility of utilising his 

 talents to intervene advantageously in human affairs. 

 A moral purpose in life was found, and thenceforth 

 Metchnikoff became an optimist and a scientific 

 philanthropist. His future researches, although 

 conducted in the laboratory, were essentially directed 

 towards the improvement of the health and happi- 

 ness of mankind. Possibly his scientific work 

 suffered occasionally from his impatience to apply 

 results to the benefit of his fellow-creatures, for, 

 like most philanthropists, he exhibited some in- 

 tolerance of criticism of his efforts. 



In 1882 phagocytosis as a curative force was still 

 only an hypothesis, but an opportunity for 

 putting it to the test of experiment soon occurred. 

 Water fleas (Daphniaj) were observed to be subject 

 to infection by a fungus {Monosfora bicuspidata) 

 the spores of which, sharp like needles, traversed 

 the gut of the insect when introduced with food. 

 Watching the process in these transparent creatures, 

 Metchnikoff saw that, immediately after the entrance 

 of a spore into the body cavity, it was attacked by 

 mobile phagocytes and englobed. If the phagocytes 

 succeeded in digesting all the spores, the daphnia 

 recovered, otherwise the spores germinated, and the 

 fungus, spreading throughout the body, killed the 

 insect. Recovery or death depended upon the issue 

 of the battle. 



The next question to be decided was whether this 

 met"hod of defence was common to all animals. 

 That some diseases of tugher animals were attri- 

 butable to invasion by microbes had recently been 

 established, and it is explained how Metchnikoff 's 

 previous training and experience as a zoologist had 

 led to the conviction of the essential unity of struc- 

 tural plan and physiological behaviour throughout 



