THE BLOOD AND ITS FUNCTIONS 



127 



OR LEUCOCYTES THAT HAVE ENGULFED 



BACTERIA 



In those at a may be seen chains of bacteria 



such as cause blood poisoning and in those at 



b are some rod shaped bacteria. (Metschni- 



koff) 



one may have absolutely no knowledge that anything un 

 usual has happened in the 

 body. Thus, many a time 

 in our lives, these little 

 defenders have guarded us 

 from dangers about which 

 we knew nothing. Some- 

 times when this battle is 

 near the surface, the skin 

 becomes painful and in- 

 flamed, and later it may 

 burst, allowing pus to es- FI G. 68. WHITE BLOOD CORPUSCLES 

 cape. This pus is largely 

 made up of white cor- 

 puscles; they themselves 

 have died and are dis- 

 charged, but they first 

 disposed of the foreign germs that would, perhaps, have done 

 us great injury. 



When leucocytes are exhausted they merely go to pieces 

 and dissolve in the blood, the residue 

 passing out of the body through the 

 different excretory organs. 



Blood Platelets. The third kind of 



I solid body in the blood is the platelet. 



These platelets are ovoid bodies, 



about one-third the diameter of the 



led corpuscles, granular but color- 



- ; Fig. 69 c. They vary in number FIG. 69. VARIOUS BODIES 

 but are always very numerous in 

 unshed blood, 600,000 or so in a single 

 drop. These bodies disintegrate very 

 quickly after blood is drawn; so quick- 

 ly that by the time a drop can be 

 placed under a microscope for the purpose of studying them., 



FOUND IN BLOOD 

 a, red corpuscle; 6, white cor 

 puscle with fibres of fibrin 

 radiating from it; c, platelets, 

 both separated and in clus- 

 ters. 



