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» SCIENCE. 



[N. S. Vol. XXIV. No. 608, 



cobra poison— what is called an antitoxin. 

 The procedure and preparation of the 

 antitoxin is practically the same as that 

 previonsly adopted by Behring in the 

 preparation of the antitoxin of diphtheria 

 poison. Animals treated with injections 

 of these antitoxins are immune to the poi- 

 son itself when subsequently injected with 

 it, or, if already suffering from the poison 

 (as, for instance, by snake-bite), are read- 

 ily shown by experiment to be rapidly 

 cured by the injection of the appropriate 

 antitoxin. This is, as all will admit, an 

 intensely interesting bit of biology. The 

 explanation of the formation of the anti- 

 toxin in the blood and its mode of antagon- 

 izing the poison is not easy. It seems that 

 the antitoxin is undoubtedly formed from 

 the corresponding toxin or poison, and that 

 the antagonism can be best understood as a 

 chemical reaction by which the complex 

 molecule of the poison is upset, or effect- 

 ively modified. 



The remarkable development of Metch- 

 nikoff 's doctrine of phagocytosis during the 

 past quarter of a century is certainly one 

 of the characteristic features of the activity 

 of biological science in that period. At 

 first ridiculed as ' Metchnikoffism, ' it has 

 now won the support of its former adver- 

 saries. 



For a long time the ideal of hygienists 

 has been to preserve man from all contact 

 with the germs of infection, to destroy 

 them and destroy the animals conveying 

 them, such as rats, mosquitoes and other 

 flies. But it has now been borne in upon 

 us that, useful as such attempts are, and 

 great as is the improvement in human con- 

 ditions which can thus be effected, yet we 

 can not hope for any really complete or 

 satisfactory realization of the ideal of es- 

 cape from contact with infective germs. 

 The task is beyond human powers. The 

 conviction has now been arrived at that, 



while we must take every precaution to 

 diminish infection, yet our ultimate safety 

 must come from within — namely, from the 

 activity, the trained, stimulated and care- 

 fully guarded activity, of those wonderful 

 colorless amoeba-like corpuscles whose use 

 was so long unrecognized, but has now been 

 made clear by the patiently continued ex- 

 periments and arguments of Metchnikoff, 

 who has named them 'phagocytes.' The 

 doctrine of the activity and immense im- 

 portance of these corpuscles of the living 

 body which form part of the all-pervading 

 connective tissues and float also in the 

 blood, is in its nature and inception op- 

 posed to what are called the 'humoral' and 

 'vitalistic' theories of resistance to infec- 

 tion. Of this kind were the beliefs that 

 the liquids of the living body have an in- 

 herent and somewhat vague power of re- 

 sisting infective germs, and even that the 

 mere living quality of the tissues T\^as in 

 some unknown way antagonistic to foreign 

 intrusive disease-germs. 



The first eighteen years of Metchnikoff 's 

 career, after his undergraduate course, 

 were devoted to zoological and embryolog- 

 ical investigations. He discovered many 

 important facts, such as the alternation of 

 generations in the parasitic worm of the 

 frog's lung — Ascaris nigrovenosa — and the 

 history of the growth from the egg of 

 sponges and medusge. In these latter re- 

 searches he came into contact with the won- 

 derfully active cells, or living corpuscles, 

 which in many low forms of life can be 

 seen by transparency in the living animal. 

 He saw that these corpuscles (as was in- 

 deed already known) resemble the well- 

 known amoeba, and can take into their soft 

 substance (protoplasm) at all parts of their 

 surface any minute particles and digest 

 them, thus destroying them. In a trans- 

 parent water-flea Metchnikoff saw these 

 amoeba-like, colorless, floating blood-cor- 



