Since such an ordinary circumstance as a hearty meal can materially influence the numbers of the white corpuscles, it would appear that they must be usually undergoing rapid variations in their number - probably by their being constantly used up and periodically replaced by new ones. The places in which they occur in greatest number are the lymphatic glands, the spleen, and the lymph follicular tissue in the intestinal tract.
There is no doubt that the lymph contains a much larger proportion of these cells after it has passed through the lymph glands, and the blood coming from the spleen contains an excessive proportion of them.
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 reproduction by division, other than that which probably 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 a tissue whose vitality has in any way suffered. During the growth of all tissues these cells seem to contribute active agents to 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 material, and some even settle themselves as permanent inhabitants of the lacunae.
Further, they are in all probability the means of renewing the red discs. Their protoplasm either takes up the coloring matter from its surroundings, or forms it within itself from suitable ingredients. Certain it is that cells are found which are recognizable as white blood cells, which have more or less of the red coloring 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.