September 14, 1893J 



NA TURE 



471 



this part, therefore, where there is a dark band of absorption, 

 the bacteria which want oxygen are attracted in crowds. The 

 motive which brings them together is their desire for oxygen. 

 Let us compare other instances in which the source of attrac- 

 tion is food. 



The Plasmodia of the myxomycetes, particularly one which 

 has been recently investigated by Mr. Arthur Lister,' may be 

 taken as a typical instance of what may be called the chemical 

 allurement of living protoplasm. In this organism, which in 

 the active state is an expansion of labile living material, the 

 delicacy of the reaction is comparable to that of the sense of 

 smell in those animals in «hich the olfactoiy organs are adapted 

 loan aquatic life. Just as, for example, the dogfish is attracted 

 by food which it cannot see, so the Plasmodium of Badhamia 

 becomes aware, as if it smelled it, of the presence of its food — 

 a particular kind of fungus. I have no diagram to explain 

 this, but will ask you to imagine an expansion of living mate- 

 rial, quite structureless, spreading itself along a wet surface; 

 that this expansion of transparent material is bounded by an 

 irregular coast- line ; and that somewhere near the coast there 

 has been placed a fragment of the material on which the Bad- 

 hamia feeds. The presence of this bit of Stereum produces an 

 excitement at the part of the Plasmodium next to it. Towards 

 this centre of activity streams of living material converge. Soon 

 the afflux leads toan outgrowth of the Plasmodium, which in a 

 few minutes advances towards the desired fiagment, envelopes, 

 and incorporates it. 



May 1 give you another example also derived from the physio- 

 logy of plants ? Very shortly after the publication of Engel- 

 mann's observations of the attraction of bacteiia by oxygen, 

 Pfeffer made the remarkable discovery that the movements of 

 the antherozoids of ferns and of mosses are guided by impres- 

 sions derived from chemical sources, by the allurement exercised 

 upon them by certain chemical substances in solution — in one 

 of the instances mentioned by sugar, in the other by an organic 

 acid. The method consisted in introducing the substance to be 

 tested, in any required strength, into a minute capillary tube 

 closed at one end, and placing it under the microscope in water 

 inhabited by antherozoids, which thereupon showed thdr pre- 

 dilection for the substance, or the contrary, by its effect on their 

 movements. In accordance with the principle followed in 

 experimental psychology, Pfeffer - made it his object to deter- 

 mine, not the relative effects of different doses, but the smallest 

 perceptible increase of dose which the organism was able to 

 delect, with this result — that, just as in measurements of the 

 relation between stimulus and reaction in ourselves we find that 

 the sensational value of a stimulus depends, not on its absolute 

 intensity, but on the ratio between that intensity and the pre- 

 vious excitation, so in this simplest of vital reagents the same 

 so-called psycho- physical law manifests itself. It is not, how- 

 ever, with a view to this interesting relation that I have referred 

 to Pfeffer's discovery, but because it serves as a centre around 

 which other phenomena, observed alike in plants and animals, 

 have been grouped. As a general designation of reactions of 

 this kind Pfeffer devised the term Chemotaxis, or, as we in 

 England prefer to call it, Chemiotaxis. Pfeffer's contrivance 

 for chemiotactic testing was borrowed from the pathologists, 

 who have long used it for the purpose of determining the relation 

 between a great variety of chemical compounds or products, 

 and the colourless corpuscles of the blood. I need, I am sure 

 make no apology for referring to a question which, although 

 purely pathological, is of very great biological interest — the 

 theory of the process by which, not only in man, but also, as 

 Metschnikoff has strikingly shown, in animals far down in the 

 .scale of development, the organism protects itself against such 

 harmful things as, whether particulate or not, are able to pene- 

 trate its framework. Since Cohnheim's great discovery in 1867 

 we have known that the central phenomenon of what is termed 

 by pathologists inflammation is what would now be called a 

 chemiotactic one ; for it consists in the gathering together, like 

 that of vultures to a carcase, of those migratory cells which 

 have their home in the blood stream and in the lymphatic sys- 

 tem, to any point where the living tissue of the body has been 

 injured or damaged, as if the products of disintegration which 

 are set free where such damage occurs were attractive to them. 



The fact of chemiotaxis, therefore, as a constituent pheno- 



' Lister. "Ontlie Plasmodium of BaMamia ulrkularis. See." Annals 

 of Botany, No. 5, Jvinp, 18S8. 



- PfefTcr, Unt^ruuh a. d. bolan. Institule z. Tubingen, vol. i., part 3, 



NO I 246 VOL. 48] 



menon of the process of inflammation, was familiar in patho- 

 logy long before it was understood. Cohnheim himself 

 attributed it to changes in the channels along which the cells 

 moved, and this explanation was generally accepted, though 

 some writers, at all events, recognised its incompleteness. But 

 no sooner was Pfeffer's discovery known than Leber,' who for 

 years had been working at the subject from the pathological 

 side, at once saw that the two processes were of similar nature. 

 Then followed a variety of researches of great interest, by 

 which the importance of chemiotaxis in relation to the destruc- 

 tion of disea.-^e-producing microphytes was proved, by that of 

 Buchnet- on the chemical excitability of leucocytes being among 

 the most important. Much discussion has taken place, as many 

 present are aware, as to the kind of wandering cells, or leu- 

 cocytes, which in the first instance attack morbific microbes, 

 and how they deal with them. The question is not by any 

 means decided. It has, however, I venture to think, been 

 conclusively shown that the process of destruction is a chemical 

 one, that the destructive agent has its source in the chemiotactic 

 cells — that is, cells which act under the orders of chemical 

 stimuli. Two Cambridge observers, Messrs. Kanthack and 

 Hardy,' have lately shown that, in the particular instance which 

 they have investigated, the cells which are most directly con- 

 cerned in the destruction of morbific bacilli, although chemio- 

 tactic, do not possess the power of incorporating bacilli or 

 particles of any other kind. While, therefore, we must regard 

 the relation between the process of devitalising and that of 

 incorporating as not yet sufficiently determined, it is now no 

 longer possible to regard the latter as essential to the former. 



There seems, therefore, to be very little doubt that chemio- 

 tactic cells are among the agents by which the human or ai.imal 

 organism protects itself against infection. There are, however, 

 many questions connected with this action which have not yet 

 been answered. The first of these are chemical ones — that of 

 the nature of the attractive substance and that of the process by 

 which the living carriers of infection are destroyed. Another 

 point to be determined is how far the process admits of adapta- 

 tion to the particular infection which is present in each case, 

 and to the state of liability or immunity of the infected indi- 

 vidual. The subject is therefore of great complication. None 

 of the points I have suggested can be settled by experiments in 

 glass tubes such as I have described to you. These serve only 

 as indications of the course to be followed in much more 

 complicated and difficult investigations — when we have to do 

 with acute diseases as they actually affect ourselves or animals 

 of similar liability to ourselves, and find ourselves face to face 

 with the question of their causes. 



It is possible that many members of the Association are not 

 aware of the unfavourable — I will not say discreditable — position 

 that this country at present occupies in relation to the scientific 

 study of this great subject — the causes and mode of prevention 

 of infectious diseases. As regards administrative efficiency in 

 matters relating to public health England was at one time far 

 ahead of all other countries, and still retains its superiority ; 

 but as regards scientific knowledge we are, in this subject as in 

 others, content to borrow from our neighbours. Those who 

 desire either to learn the methods of research or to carry out 

 scientific inquiries, have to go to Berlin, to Munich, to Breslau, 

 or to the Pasteur Institute in Paris, to obtain what England 

 ought long ago to have provided. For to us, from the spread 

 of our race all over the world, the prevention of acute infectious 

 diseases is more important than to any other nation. At the 

 beginning of this address I urged the claims of pure science. If 

 I could, I should feel inclined to speak even more strongly of 

 the application of science to the discovery of the causes of 

 acute diseases. May I express the hope that the effort which 

 is now being made to establish in England an institution for 

 this purpose not inferior in efficiency to those of other countries, 

 may have the sympathy of all present? And now may I ask 

 your attention for a few moments more to the subject that more 

 immediately concerns us ? 



Conclusion. 

 Thepurpose \yhich I have had in view has been to show that 

 there is one principle — that of adaplation^which separates 



-' H!'*''' " '''' Anhiiufung der Leuc->cylen am One des Entziindungs- 

 reizes." &c., Die Entstehung dcr Enztiindung, &c., pp. 423-464 Leipag, 

 1891. 



•■' Buchner, "Diechem. Reiibarkeit der Leucocyten," &c., Berliner klin 

 Woch., 1890, No. 17. 



3 Kanthack and Hardy, " On the Characters and Behaviour of the Wan- 

 dering Cells of the Frog," Proceedings of the Royal Society, vol. Hi., p. 367. 



