254 [Recess, 



a thin layer of blood, the corpuscles of which will form themselves 

 into the most perfect and beautiful rouleaux. 



The plasticity of the blood-corpuscle is unrivalled by any other 

 physical body. It will assume all sorts of protean shapes under 

 the slightest influences. Elongating to a mere thread, it will pass 

 through a narrow chink ; it will wrap itself round an acute projecting 

 angle, or protrude feelers and tails under the influence of currents. 

 In its natural state it possesses sufficient elasticity to resume its 

 original shape on the cessation of modifying influences ; but when 

 gum or gelatine has been added, or when the plasma has been per- 

 mitted to thicken spontaneously, the corpuscle retains any form it 

 may have assumed, till again altered by some fresh influence. 



The only artificial body capable of simulating the visible modifi- 

 cations of the ^blood-corpuscle is an extremely delicate, moderately 

 filled vesicle. 



The variations in its behaviour appear to be due to the degree of 

 distention or flaccidity, which are doubtless under the influence of 

 diosmosis. 



When the corpuscles are apparently fused together, as after the 

 addition of gum, the mass runs about like a thick liquid. Parts not 

 previously in contact coalesce intimately with each other. Under 

 the influence of currents, these masses stretch at certain points into 

 fine threads, consisting of a single file of corpuscles, each corpuscle 

 being elongated to its utmost, and finally sever at the natural 

 junction of a single corpuscle with its fellow, the two stretched por- 

 tions receding again into their respective masses. 



Familiarity with the various conditions which the blood-corpuscles 

 assume, and the analogous effects which take place in globules of 

 homogeneous liquids, leads irresistibly to 1 the conclusion that, on 

 account of their great plasticity and the extreme tenuity and pliancy 

 of their enclosing membrane, the blood- corpuscles are, under certain 

 circumstances, subject to the law of cohesive attraction, in- the same 

 manner as these globules j and that, as with the latter so with the 

 blood-corpuscles, changes in the character of the surrounding liquid 

 determine the facility with which this law may come into operation. 



If, as is well known, we place on a non-metallic surface small 

 portions of liquid mercury, they will retain their spheroidal shape ; 

 and if any two of them be made to touch, they will be attracted to 



