1869.] Dr. Norris on the Aggregation of Blood- corpuscles. 431 



3. Irritation, by reducing the vitality of the surrounding tissues, causes 

 them to bear the same relation to the blood within the vessels in their 

 immediate vicinity as ordinary matter does to that which has been shed, 

 inducing adhesiveness of the corpuscles, and thus bringing about inGam- 

 matory stasis. 



These effects upon the blood-corpuscles are assumed by Lister to depend 

 upon chemical changes iuduced by ordinary matter or by vitally degraded 

 tissues upon the plasma of the blood ; but inasmuch as chemical changes 

 cannot occur without corresponding physical modifications, it is quite as 

 rational to refer the increased aggregating-tendency displayed by the cor- 

 puscles to physical as to chemical changes in the liquor sanguinis ; and this 

 view has the advantage of not requiring us to believe that the functional 

 activity of the tissues is depressed by mild forms of irritation — an idea which 

 is opposed to all we know of the increased nutritive and formative changes 

 which follow in the wake of irritation. 



Having now briefly reviewed the existing position of the subject, we 

 will proceed to consider the real causes at work in the production of the 

 phenomenon under consideration. 



Many years since, having familiarized myself with the behaviour of, and 

 the appearances presented by blood-corpuscles under almost every con- 

 ceivable "condition, both within and without the vessels, I became pro- 

 foundly impressed with the conviction that these phenomena had their 

 origin in some physical law of attraction, and at the same time felt not the 

 less certain that, if this view proved to be correct, the behaviour of the 

 blood-corpuscles would be found to be no isolated exhibition of this law, 

 and that, provided conditions similar to those which exist in the case of 

 the blood-corpuscles could be obtained, many illustrative examples of the 

 operation of the law would be immediately forthcoming. 



That such attractive force did not exert its influence through distances 

 readily appreciable was obvious, and this fact at once indicated that it 

 must be sought for among those forms of attraction which have been 

 designated molecular. 



After much experiment and reflection I came, in 1862, to the conclusion 

 that these phenomena were due to no less universal a law than that of 

 cohesive attraction ; and I embodied the views I then held upon the subject 

 in a paper which was read before the Royal Society, and published in the 

 Proceedings, entitled " The Causes of various Phenomena of Attraction and 

 Adhesion as exhibited in Solid Bodies, Films, Vesicles, Liquid Globules, and 

 Blood-corpuscles." Since that time other departments of physiology have 

 occupied my attention ; and I have only been induced to recur to the old 

 theme because T find that, in some recent references to the history of this 

 subject, my observations have not been mentioned, from which I .am 

 led to infer either that my views had not been sufficiently put forward, 

 or that my experiments had failed to produce conviction in others. I 

 therefore now present the result of a renewed investigation, in which I 



