BLOOD PLATELETS. 39 



the coloring matter is dissolved out. The hemoglobin is 

 ensnared in the stroma. 



(b) White Blood Corpuscles or Leucocytes. 



General Description. The white blood corpuscles or leu- 

 cocytes are large, colorless, nucleated cells with no general 

 form, but which are capable of changing their form by ameboid 

 movement. 



Number. The number of leucocytes varies from seven to ten 

 thousand per cubic millimeter. 



Function. The white corpuscles are not under the control of 

 the central nervous system, but are controlled by some chemo- 

 taxic force. They are able to go and come by ameboid move- 

 ment through the stromata of capillary walls and wander here 

 and there in the tissues. It is this that gives them their name 

 of wandering cells. 



White blood corpuscles are of importance from a physiological 

 standpoint, because of this ability to wander. They can trans- 

 fer undissolved substances from one part of the body to another 

 and can destroy and remove foreign substances and hurtful 

 microorganisms. 



The power they have of ingesting foreign substances is called 

 phagocytosis. They will migrate in large numbers and sur- 

 round a foreign object and endeavor to remove it from the tissue. 

 They have the power of liquefying tissue and it is this lique- 

 fied tissue mixed with the dead bodies of white corpuscles that 

 is known as pus. 



(3) Blood Platelets. 



These are colorless discs about one-third to one-fourth the 

 size of red blood corpuscles. Some claim for them the full 

 value of blood cells, while some claim they are the nuclear re- 

 mains of destroyed leucocytes. They are about 635,000 to one 



