Exudate and Proliferate. 267 



any existing openings. The presence of any substance with chemo- 

 tactic power determines the direction taken in the further move- 

 ments of these cells. 



The majority (about seventy per cent.) of the motile cells col- 

 lectively spoken of as leucocytes, which are found in an infiam- 

 matory focus, are characterized by the possession of multiple 

 nuclei, or one polymorphous nucleus, and very fine granulations only 

 seen in fresh specimens. These polymorphonuclear forms are re- 

 garded as the characteristic white blood cells and arise from the 

 bone marrow (where they are mononuclear, acquiring biscuit and 

 clover leaf types of nuclei only in passing into the blood as the 

 result of nuclear division or fragmentation). Besides these, which 

 are described by Ehrlich as neutrophilic leucocytes, there are met 

 in inflamed tissues forms containing coarser granules which, be- 

 cause of the readiness of their granules to take up intensely 'the 

 acid aniline dyes, like eosin, are known as eosinophile leucocytes; 

 and others with special tinctorial tendency of their coarse granules 

 for the alkaline anilines (gentian violet), known as mast cells. 

 Mononuclear (single nucleus) cells are also comparatively numer- 

 ous in inflamed tissue, the nucleus round and rich in chromatin, 

 and the cytoplasm showing as a very narrow margin about the 

 small or large nucleus. These are regarded as lymphocytes, which 

 have originated from the lymph glands or germinal lymphatic 

 centres. As above mentioned, the great increase of these cells 

 depends in part upon a chemical stimulation acting not only on the 

 blood vessel walls but also upon the foci of lymphoid cells dis- 

 tributed in all the tissues and causing enlargement of these lymph- 

 cell forming centres; and in the second place, as many of these 

 cells have come from the marrow, it may be inferred that these 

 chemical substances, which act locally in the inflammatory area as 

 chemotactic agents and stimulants to proliferation, are also present 

 in the circulating blood and with it pass into the bone marrow and 

 there exert the same influence, that is, stimulate this tissue to the 

 formation of leucocytes. Often in inflammation there is not only a 

 swelling of the lymph follicles, but even a hyperplasia or meta- 

 plasia (change of red marrow into lymphoid) of the bone marrow 

 referable to its exaggerated function. 



The causes of inflammation and the chemotactic substances set 

 free in the affected tissue have, moreover, a stimulating influence 

 upon the proliferation of the fixed eells. The endothelial cells of 

 the blood vessels and lymphatics and the connective tissue cells 

 take part in the proliferation in every inflammation, the beginning 



