484 APPLIED BIOLOGY 



The red corpuscles of man and other mammals have no 

 nuclei, except in embryonic stages ; but all lower vertebrates 

 birds, reptiles, amphibia, and fishes have nuclei in all 

 red corpuscles, even in the adult animals. Scientists have 

 not yet found any reason for this difference. 



It is also interesting to know that red corpuscles are con- 

 stantly being formed in the red marrow of bones. Obtain a 

 long bone from a meat-market, break it open, and examine 

 the marrow. 



The white corpuscles are irregular in shape, because they 

 move spontaneously like the Amceba ( 270). In human 

 blood they occur in the proportion of one white to 700 of the 

 red cells. They are exceedingly abundant in blood taken 

 from any inflamed place, such as a boil, pimple, or wound. 

 Like the Amceba, which they resemble, although there is no 

 connection as to origin, the white cells can engulf (" eat ") 

 small particles, such as bacteria, by the flowing of the pro- 

 toplasm around the object. It is believed that their work or 

 function is that of destroying bacteria and particles of dead 

 cells. This explains why they are abundant in such places 

 as boils and abscesses. The material known as pus, which 

 exudes from such centers of inflammation, contains numerous 

 white corpuscles and many particles from the dead cells of 

 the inflamed tissue. 



(D) Examine a drop of human blood spread on an object-slide and 

 protected with a cover-glass. A drop may be obtained by wrapping 

 a piece of string tightly around a finger near its end and then prick- 

 ing the skin with a needle which is first made sterile by passing 

 several times through a flame. One small drop of blood should be 

 placed in a drop of normal salt solution (common salt 7 grams in a 

 liter of water, which gives 0.7 per cent). The red corpuscles appear 

 faint yellow in color when not in masses. The rarer white cells are 

 difficult to find, but may be located by turning the micrometer screw 

 about half a revolution so as to throw the red corpuscles slightly out 

 of clear focus, and then a few white cells may be seen as glistening 

 points of light in the field. They are somewhat larger than the red cells. 



