10 



times ^ I refer to the dilatation and relaxed condition of the 

 vessels, the slowing of the blood stream, the falling out of the 

 colourless corpuscles, like tired soldiers on the march, as Pro- 

 fessor Burdon Sanderson has expressed it, their leaving the mid- 

 stream and loitering against the vein wall, afterwards sticking 

 to it, and then in some wonderful way wandering out, emigrating 

 through the unbroken vascular wall into the surrounding space, 

 some of them becoming disintegrated and dissolved in the liquid 

 which is also effused, and so leading to an accumulation of 

 coagulable lymph or inflammatory exudation external to the 

 vessels. How much is there in these phenomena which still 

 requires investigation and explanation ! Why do the blood- 

 vessels dilate 1 how is the emigration of the colourless corpuscles 

 to be explained 1 by what means also, do these corpuscles " pene- 

 trate into dead tissue and indeed into any material capable of 

 imbibition with which they are brought into contact in an active 

 state '"2 And then the further questions may be suggested: 

 Does there exist an antagonism or attraction between these white 

 corpuscles and those recently discovered organisms the bacilli? 

 Is there a struggle for existence between them 1 How are the 

 powers, and action, and growth of the colourless corpuscles 

 modified by the presence of these micro-organisms? What part 

 do the latter play in the production of disease ? Is it true that a 

 large part of all health and disease in the world is dependent 

 upon them 1 Such questions as these indicate the degree of 

 importance which must be assigned to the discovery of these 

 bodies, and account for the interest in them which prevails at 

 the present time. Probably no other discovery since that of the 

 circulation of the blood ap})ears to be so full of promise iu 

 elucidating the causes and courses of some diseases as this one. , 



