1862.] 257 



respect by variations in the surrounding medium. They may also, 

 by disturbances of this medium, become elongated ; and if the elon- 

 gated mass severs, each portion falls back into itself and becomes an 

 independent globule. They also become adherent to the solids which 

 they touch, and exhibit tail-like processes. It will be universally 

 admitted that these latter phenomena depend on cohesive attraction. 

 Compared with the blood-corpuscles, these bodies are rigid and un- 

 yielding ; how much more readily may we therefore ascribe the like 

 effects observed in the former to the same cause. 



It has been urged that nothing approaching to the character of an 

 attractive influence has ever been observed with the blood-disks ; but 

 it must be remembered that the attraction of cohesion could not be 

 indicated by motion between corpuscles at perceptible distances, but 

 could only take place when the particles of the bodies were so closely 

 applied to each other as to be within the radius of the sphere of 

 molecular influence ; and it is only under certain special circum- 

 stances that such an attraction could be even inferentially visible. 



I have repeatedly observed such an attraction exercised among 

 corpuscles under the only circumstance in which the observation is 

 possible. After the addition of gum or gelatine to the blood, and 

 the cessation of the consequent disturbance, there will still be many 

 individual corpuscles and little circular masses floating sluggishly 

 and unattached in the serum. After a time some of these will come 

 in contact with each other at one point in their circumference ; and if 

 the disturbance in the liquor sanguinis is very slight, they will cohere 

 at this point, and then will be seen to become gradually applied to 

 each other for half their circumference. This is an action which can 

 readily be understood as the successive operation of molecular attrac- 

 tion on the particles of the corpuscles immediately contiguous to 

 those in absolute contact, but can receive no explanation on the 

 hypothesis of adhesiveness. The best mode of observing this im- 

 portant phenomenon is to draw the mixture of gum and blood 

 between two glasses in contact. 



