RED CORPUSCLES. 145 



ber per cubic millimeter calculated. A diminished number is of clinical 

 importance. 



The duration of the life of mature red corpuscles is unknown, but is 

 supposed to be brief. They may be devoured intact by phagocytes, but 

 generally they first break into numerous small granules. These may be 

 ingested by certain leucocytes, or by the peculiar endothelial cells of the 

 liver. Their products are thought to be eliminated in part as bile pig- 

 ment. The destruction of red corpuscles occurs especially in the spleen 

 and haemolymph glands; to a less extent in the lymph glands and red bone 

 marrow. Pigmented cells in some of these structures derive their pig- 

 ment from destroyed corpuscles. Sometimes a 'stippling' or granule 

 formation occurs within the corpuscle, which has been ascribed to degenera- 

 tion of the haemoglobin. The dissolution of red corpuscles is known 

 as haemolysis and follows the injection of certain poisonous substances 

 into the blood. It occurs in various diseases. The study of the effects 

 of mixing the blood of one species of animal with that of another has pro- 

 vided a very perfect means of distinguishing the species from which a 

 blood stain of unknown origin may have been derived. Such studies are 

 not histological, however. 



The account of the mammalian red corpuscles may be summarized 

 as follows. Ery throb lasts with large reticular nuclei, cell membranes, 

 and a protoplasmic net, are the first blood cells in the embryo. They 

 multiply by mitosis in the circulating blood, and most of them by acquiring 

 small dense nuclei become normoblasts. Haemoglobin has meanwhile 

 developed in their protoplasm which loses its reticulum. The mem- 

 brane is no longer well defined. The nucleus after more or less fragmen- 

 tation becomes either absorbed or extruded from the cell, which thereupon 

 is cup shaped. The cups are flexible and very susceptible to osmotic 

 changes, swelling or shrinking with alterations in the density of the sur- 

 rounding plasma. They are destroyed by dissolution or fragmentation, 

 and are often devoured by phagocytic cells. From them pigments with or 

 without iron are developed. The red corpuscles in the adult are formed 

 chiefly in the red bone marrow, and are destroyed especially in the spleen 

 and haemolymph glands; some of their products are eliminated in the bile. 



White corpuscles. The leucocytes are those blood cells which retain 

 their nuclei and do not contain haemoglobin. About eight thousand 

 occur in a cubic millimeter of human blood. If their number exceeds 

 ten thousand the condition is called leucocytosis and becomes of clinical 

 importance. There exists, therefore, normally but one leucocyte for five 

 or six hundred red corpuscles. In the circulating blood the two sorts are 

 said not to be evenly mixed; the leucocytes are more numerous in the 



