36 Colonel Sir Almroth E. Wright [March 9, 



make their way to every focus of infection ; that they ingest microbes 

 when these have first been prepared by the action of the blood fluids ; 

 and, finally, that they can, if things go favourably, digest and 

 dissolve the ingested microbes. There Avould, by consequence, in 

 connexion with the leucocyte, be three functions to study. First 

 would come emigration, then phagocytosis, and lastly intracellular 

 digestion. Emigration has up to the present been studied only in 

 the interior of the organism. You will realise that means that it 

 has been studied only in a difficult setting and in the presence of all 

 manner of disturbing factors, and you will appreciate that we want now 

 a new and better technique. For we require for the treatment of 

 the infected wound to find out how best to call out the leucocytes ; 

 and how, when occasion requires, to restrain their emigration. 



I have in connexion with this a technique to describe to you ; but 

 first I want you to appreciate what we can and what we cannot expect 

 from leucocytes in the matter of locomotion. Leucocytes can, we 

 know, make their way out through small openings. They can also 

 travel over any ordinary surface. They can edge their way along 

 faster w^hen lightly compressed between two surfaces. They can 

 crawl along strands, creep through a mesh work, and climb a scaffold- 

 ing. But they are unable to climb a vertical glass wall. And again, 

 they are unable to swim, and so once they get into open fluid they 

 simply go to the bottom. We may liken them to very minute slugs 

 crawling along surfaces and climbing trellises, but brought up short 

 by any considerable barrier of fluid. 



All these points must be considered when seeking for a technique 

 for the experimental study of emigration, using for that study 

 specimens of blood withdrawn from the body. The containing blood- 

 vessel can up to a point be imitated by a glass tube, and we can, to 

 facilitate observation, use tubes drawn out flat, such as shown in 

 Fig. 4. But the artificial differs from our natural capillary in having 

 impermeable instead of permeable walls. This, of course, makes 

 emigration through the walls impossible. None the less, these tubes 

 supply what we want for the study of the movements of leucocytes. 

 We can institute races along the length. 



But first certain preparations must be made. The course must 

 be cleared of all obstructions — i.e., the red corpuscles must be got 

 out of the way. Xext the leucocytes must all be brought back behind 

 the scratch line. Further, we must provide a scaffolding for the 

 leucocytes to climb. All this can be arranged. We fill in our flat 

 emigration tuljes with blood and seal them at one end. Then, by 

 centrifuging, we l)ring the blood fluids to the top and the corpuscles 

 to the bottom. The lighter leucocytes will now have arranged them- 

 selves in a layer immediately above the red ; and presently the super- 

 natant fluid will clot and the mesh work of fibrin will then provide 

 the scaffolding we require. We can now impose upon the clot— let 

 me for convenience call it the white clot — any chemical agent we 



