432 Dr. Norris on the Aggregation of Blood-corpuscles. [May 27, 



believe I have established, by conclusive experiments, the correctness of 

 my explanation of the phenomena. 



Among the various modes of aggregation which the blood-corpuscles 

 undergo, two typical forms stand prominently forward, of which all others 

 are merely modifications. The one appears to be dependent upon the 

 normal disk-shape, the other upon the globular or spherical form which 

 the corpuscles assume on the addition of various substances to the blood, 

 Such as gum, gelatine, linseed mucilage, potash, &c. 



With the first of these modes of aggregation, viz. into rouleaux, we are 

 all sufficiently familiar ; and an excellent notion of the character of the 

 second form may be obtained by a careful examination of microphoto- 

 graphs of the blood-corpuscles which have been obtained instantaneously by 

 exploding magnesium in heated oxygen*. 



In order to leave as little as possible to hypothesis, it was desirable as 

 a preliminary step to make sure that these differences in form of the cor- 

 puscles were the real cause of the diverse modes of arrangement — whether, 

 in fact, we could safely predicate that disk-shaped bodies having an attrac- 

 tion for each other would arrange themselves so as to form rolls or cylin- 

 drical masses, and whether, on the other hand, attracting spheres of soft 

 material would attach themselves together in such a fashion as to cause 

 plane surfaces to be opposed to each other — in a word, to convert them- 

 selves by mutual attraction into polyhedral bodies just as they might do 

 under mutual compression. 



In the first place, we had to ascertain experimentally how disk-shaped 

 bodies, having the utmost freedom of movement, and possessing an attrac- 

 tion for each other, would arrange themselves. 



In casting about for the conditions to make such an experiment, I re- 

 membered a very familiar phenomenon which had often excited my curi- 

 ositv, viz. the rapidity with which a bubble or a small floating fragment upon 

 the surface of a cup of tea or other liquid rushes to the side of the con- 

 taining vessel, or with which two such bubbles or fragments rush together, 

 the moment they approach within a certain range. I determined to see if 

 I could not make use of this attraction, the true nature of which I at the 

 time imperfectly understood, and with this object prepared a number of 

 circular disks of cork, which I accurately poised so that they should 

 assume and maintain the vertical position when partially immersed in 

 liquid. On throwing these disks into liquid, I had the satisfaction of 

 seeing them run together and form themselves into the most perfect 

 rouleaux after the fashion of the blood-disks. 



This experiment has the value of demonstrating that if the blood- 

 disks attracted each other, their shape would determine the formation of 

 rouleaux. 



As regards the behaviour of spherical vesicles or globules which attract 



* Specimens of these, as well as the several experiments referred to in the paper, were 

 exhibited to the Society. 



