MIGRATION OF WHITE CORPUSCLES. 45 



their substance the black particles which were in 

 contact with them ; and when by their amoeboid 

 movements from one place to another they are 

 brought into contact with other particles these also 

 are in like manner absorbed. On careful watching 

 it may be made out that the process of intussuscep- 

 tion commences by the throwing out of processes 

 which surround the particle to be taken in, and 

 meet and coalesce beyond it ; once included in this 

 manner, the grannie afterwards becomes gradually 

 carried, presumably by the movements of the proto- 

 plasm, more towards the centre. If, after observing 

 the preparation in this way for half an hour, it be 

 laid aside for two or three hours, it will be found at 

 the expiration of that time that many of the white 

 corpuscles have taken in a large number of the black 

 particles, for they do not discharge their cargo, but 

 carry it about in their movements from place to 

 place. 



This property of the white blood-corpuscles has been 

 used in pathological investigations to determine the 

 source of the corpuscles of pus, which resemble the white 

 corpuscles of the blood. Insoluble particles were in- 

 jected into the bloodvessels of an animal, and inflamma- 

 tion was induced at a special part: it was found that the 

 pus-corpuscles which accumulated outside the blood- 

 vessels in the inflamed part contained similar particles. 

 The corpuscles must consequently have come from the 

 blood, for such particles have not the power of passing 

 through the coats of the bloodvessels unless carried by 

 the white corpuscles. 



Preparation 10. Migration of White Cor- 

 puscles. The process of migration can be quite 

 easily seen in progress in transparent parts of 

 animals, and will be afterwards studied when the 

 methods of observing the circulation of the blood 

 are described. But for exhibiting the active migra- 

 tion of the white blood-corpuscles nothing is more 

 striking than the examination of a capillary tube in 



