Page:The Harveian oration 1888.djvu/18

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 Professor 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 " penetrate 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? 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 in elucidating the causes and courses of some diseases as this one.