In normal blood the red blood corpuscles predominate. They are all similar in form and, with few exceptions, of the same size. They stain strongly with acid solutions such as eosine. In pathological conditions, large or giant corpuscles may be found (macrocytes), as well as those of medium size (normal) and small size (microcytes). Some are vigorous and stain deeply; others, on the contrary, are degenerating or dead, and have no greater affinity for one constituent than for another of the double or triple stains commonly employed.
In pathological conditions the hæmatoblasts occur in very varying numbers.
The white blood corpuscles found in health may be classified as follows:—
Large and small lymphocytes, each of which has a round voluminous nucleus and a narrow border, and contains a non-granular protoplasm; their proportion varies between 22 per cent. and 25 per cent.:
Polynuclear leucocytes or polymorphous leucocytes with a single nucleus, which originate in bone marrow, stain best with neutral colours, and are present in the proportion of 70 per cent. to 72 per cent.:
Mononuclear leucocytes with an ovoid eccentric nucleus stain best with basic colours, and form about 1 per cent.:
Polynuclear leucocytes stain best with eosine or acid colours, and form about 1 per cent. to 2 per cent.
When these white blood corpuscles are in larger number the condition is known as leucocytosis, and when one or other variety is in very great excess the condition is known as leucæmia.