18 THE ESSENTIALS OF HISTOLOGY 



The amoeboid phenomena which are exhibited by the protoplasm of 

 the colourless blood-corpuscles consist, in the first place, of spontaneous 

 changes of form, which, when active may also produce changes in place 

 or actual locomotion (migration) of the corpuscle ; and, secondly, of a 

 tendency which it presents to enwrap and take into its substance 

 foreign particles with which it may come in contact, and particles thus 

 incepted may then be conveyed by the corpuscle in its locomotory 

 changes from one place to another. 



It is probable that particles of organic matter which are taken up 

 by the pale corpuscles may undergo some slow process of intracellular 

 digestion within their protoplasm. 



The processes of the granular corpuscles are generally quite clear 

 at first, and. the granules afterwards flow into them. 



The migration of the colourless corpuscles from the blood-vessels 

 into the surrounding tissue, or from a blood-clot into the surrounding 

 serum (fig. 16), is owing to these amoeboid properties. 



The conditions which are most favourable to this amoeboid activity 

 of the white corpuscles are (1) the natural slightly alkaline medium, 

 such as plasma, serum, or lymph, or, failing these, normal saline 

 solution ; (2) the prevention of desiccation. Any increase of density 

 of the medium produces a diminution of amoeboid activity, whilst, on 

 the other hand, a slight decrease in its density has the opposite effect ; 

 (3) a certain temperature. In warm-blooded animals the phenomena 

 cease below about 10 C. When gradually warmed they become more 

 and more active up to a certain point, the maximum being a few 

 degrees above the natural temperature of the blood. Above this point 

 they become spheroidal and their protoplasm is coagulated and killed. 

 Acids at once kill the corpuscles and stop the movements. Narcotic 

 gases and vapours, such as carbonic acid gas or chloroform vapour, 

 also arrest the movement, but it recommences after a time if their 

 action is discontinued. 



