54 ADAPTATION AND DISEASE 



ally take these up freely and digest them. As I have pointed out 

 elsewhere, 1 while MetchnikofE, perhaps naturally, minimized the 

 part played by other factors in the inflammatory process, the 

 fact remains that phagocytosis and the acquirement of phago- 

 cytic powers play a highly important part in the successful 

 resistance to infection. As shown by Sir William Leishman's 

 simple and beautiful experiment (which formed the basis of Sir 

 Almroth Wright's opsonic technique), there is not one pathogenic 

 microbe which cannot be shown to be taken up and digested 

 sooner or later by the polymorphonuclear leucocytes of the 

 human blood. 



Into the more intimate mechanism of this and other acquire- 

 ments I purpose to enter in the concluding lecture of this series. 



In the next place, to carry on my argument, it is to be observed 

 that this is not a temporary acquirement by the individual. 

 The length of time during which the organism continues to 

 elaborate actively these new " antibodies " varies, it is true, 

 according to the micro-organism, but in all cases the amount 

 elaborated is over and above the amount of " antigen " involved, 

 and the production continues long after the antigen, be it toxin 

 or be it bacterial bodies, is used up. For months after a man 

 has been given one or two doses of dead typhoid bacilli his blood 

 serum either contains specific antibodies — agglutinins — or has 

 a different physical constitution ; and in some cases where there 

 is not artificially but naturally acquired immunity, that is to 

 say where a man has gone through a severe attack of typhoid 

 fever, agglutinating power has been noted for five years and 

 more after recovery. In fact, this retention of properties by 

 the inoculated or vaccinated men has necessitated the develop- 



1 Inflammation, an Introduction to the Study of Pathology, being the 

 reprint (revised and enlarged) of an article in Sir T. Clifford Allbutt's System of 

 Medicine, 4th ed., Macmillan & Co., Ltd., 1909. This gives an epitome of 

 MetchnikofFs observations. I had the good fortune to be working in Metchni- 

 kofi's laboratory at the Institut Pasteur in the winter of 1890, at the time when 

 he gave his first comprehensive review of his studies upon Phagocytosis and 

 their bearing upon Inflammation, Infection, and Immunity. With his per- 

 mission I translated the lecture and published it in the British Medical Journal, 

 1891. Following the publication of the lecture I remember that I had a 

 correspondence with Sir J. Burdon Sanderson in the pages of that journal. 

 It is curious to-day to recall that he could not accept the phagocytosis 

 theory of immunity, on the ground that the education and adaptation of 

 the leucocyte demanded an individual intelligence on the part of the individual 

 cell. 



