1869.] Dr. Norris on the Aggregation of Blood-corpuscles. 435 



The explanation is equally easy if we accept the old and, I believe, the 

 true view, of the vesicular character of these bodies, as we have only to 

 assume that the envelope is so saturated with the corpuscular contents 

 as practically to act as such contents would themselves act, i. e. to exhibit 

 a greater cohesive attraction for their own particles than for those of the 

 contiguous liquid. 



The cohesive power of the blood-corpuscles varies with varying conditions 

 of the liquor sanguinis ; and this is doubtless due to the law of osmosis ; 

 for we can readily imagine that when the exosmotic tendency is in excess, 

 the corpuscles will become more adhesive, and, on the contrary, when the 

 endosmotic current prevails, less so. In any case the increased cohesive- 

 ness will be due to the increased extrusion of the corpuscular contents 

 upon the surface. 



All, then, that is required in the case of the blood-corpuscles, is a differ- 

 ence between their liquid contents and the plasma in which they are sub- 

 merged. That this difference is not so great as between the liquids used 

 in these experiments is probable ; but it must also be remembered that the 

 attraction is not so powerful. The power required to attach the blood- 

 corpuscles together is, on account of their exceeding minuteness, extremely 

 small, as they are thus so much more removed from the influence of gravi- 

 tation, and brought under that of molecular attraction. 



I shall conclude this paper by a brief reference to inflammatory stasis. 

 In one of my papers (communicated to the Royal Society in 1862) I described 

 no. less than four distinct forms of stasis. I proposed to designate that in- 

 duced by irritation homogeneous stasis, because the blood-corpuscles be- 

 come so blended together as to entirely lose their outlines and present the 

 appearance of a uniform and continuous plug filling up the capillaries. 



This peculiar blending of the corpuscles is dependent upon the law I 

 have been describing, viz. that of double cohesion, and is brought about 

 by diminished quantity of liquor sanguinis in a part in proportion to the 

 corpuscles, and by loss of fluidity in that which remains. 



One of the primary effects of irritation is neural paralysis of the minute 

 arteries which supply capillary tracts ; and this paralysis gives rise to 

 increased diosmotic action, in fact to exudation of liquor sanguinis ; conse- 

 quently there is a lagging behind of the corpuscles, and an increase of their 

 numbers in the capillaries ; the plasma, too, which still surrounds the cor- 

 puscles in the capillaries, is modified ; and when a certain relation has been 

 reached between the corpuscles and the plasma, the former blend together 

 precisely in the same manner as the soap-bubbles, or as the blood-corpuscles 

 exhibited in the photographs. This completely arrests the passage of 

 blood through the capillaries, which become as much occluded as if blocked 

 up by solid fibrin. 



1 have frequently had opportunities of watching in the transparent webs 

 of frogs the mode in which this homogeneous stasis is resolved. In these 

 creatures the restoration of the circulation commences some hours after the 



VOL. XVII. 2 K 



