THE RED CORPUSCLES. 231 



It is then not unreasonable to suppose that many of the white 

 cells found in the blood have their origin in these organs. 



They may also be developed from similar cells in any tissue, 

 but their multiplication by division, other than that which prob- 

 ably occurs in the lymph follicles, where it cannot be seen, is a 

 circumstance of the greatest rarity, and few observers have been 

 fortunate enough to witness the phenomenon. 



The destiny of the white blood cells is probably manifold. 

 From the readiness with which they escape from the capillaries 

 and wander by their amoeboid movement through the neighboring 

 tissues to reach any point of injury, it would appear that they 

 take an active part in the repair of any tissue whose vitality has 

 in any way suffered. During the growth of all tissues the cells 

 seem to contribute active agents in their formation ; thus in the 

 formation of bone it has been stated that escaped blood cells or 

 their immediate offspring help to lay down the calcareous mate- 

 rial, and some even settle themselves as permanent inhabitants of 

 the lacunae. 



Further, they are in all probability the means of renewing the 

 red disks. Their protoplasm either takes up the coloring matter 

 from its surroundings, or forms it within itself from suitable in- 

 gredients. Certain it is that cells are found which are recogniz- 

 able as white blood cells which have more or less of the red color- 

 ing matter imbedded in their substance. As this increases, the 

 cell gradually loses its distinctive characters and assumes those 

 of a red corpuscle. Such elements, it will be seen, are common 

 in the spleen and the blood leading from it. 



THE RED CORPUSCLES. 



The red disks were discovered in the human blood by Leuwen- 

 hoek, about 1673. They alone give the red color which charac- 

 terizes the blood of all vertebrated animals (except the amphioxus), 

 but are not found in the blood of the invertebrata, which only con- 

 tains colorless cells. When the blood of the invertebrates has a 

 color, it owes it to the fluid, not to the corpuscles. The individual 

 disks when viewed singly under the microscope appear to be pale 

 orange, but when in masses the red becomes apparent. 



