FORMATION OF MACROPHAGES BY THE CELLS LINING THE 



SUBARACHNOID CAVITY IN RESPONSE TO THE STIMULUS 



OF PARTICULATE MATTER, 



BY CHARLES R. ESSICK. 



In the course of a study of the processes involved in the localization of an 

 infection within a focus in the nervous system, certain physiological reactions of the 

 cells lining the subarachnoid space have been noted. When active or inert particles 

 of matter are injected into the subarachnoid cavity of a living animal, the cells 

 lining the space hypertrophy, lose their normal attachments, and engage in remov- 

 ing the debris. The importance of such a formation of free-living cells from fixed 

 elements in any process involving destruction and repair in the meninges (infection, 

 hemorrhage, etc.) becomes apparent. The control of cell-reaction promises much 

 in the ultimate therapy of such conditions. 



Physiological activity of cells has always been an attractive study, two functions 

 of which may be readily demonstrated in fixed preparations, i. e., phagocytosis 

 and amceboid wandering. We are accustomed to think of cells as peculiarly fitted 

 to the specialized work in which they are normally engaged ; for example, the peri- 

 toneal and pleural surfaces are membranes of cells specifically adapted to the free 

 movement of viscera; endothelium of blood-vessels forms a closed tube for con- 

 ducting the various chemicals used in tissue economy; connective tissue furnishes 

 a supporting framework, and so on. As a corollary to this idea we have to employ 

 a special set of unattached cells to remove products formed during the normal wear 

 and tear of the tissues, and to overcome and remove any noxious stimulants. 



The kaleidoscopic changes which take place in inflammation have attracted 

 many observers to the role played by the so-called fixed cells and have given rise 

 to a large number of conflicting views. It seems unnecessary, for a clear under- 

 standing of this paper, to go into these conceptions in detail. Accumulated evidence 

 leaves little doubt that, under certain conditions, the normal specialized function 

 becomes a secondary characteristic and the more primitive attributes of the uni- 

 cellular organism become the predominant features. In other words, unless a cell 

 has become too highly specialized the primitive functions of free amoeboid move- 

 ment and phagocytosis may be elicited by the proper type of stimulation in cells 

 which normally are regarded as sessile or fixed elements. The connective tissues 

 have furnished Maximow with a host of cells (polyblasts), normally sessile and in 

 fact almost indistinguishable from their neighbors; such polyblasts under stimula- 

 tion become amceboid and phagocytic. At times even the fibroblasts may round 

 up and behave toward irritants in the same way that the polyblasts do. Schott 

 (1909), confirmed by Goldmann (1912), showed that the mesothelial lining of the 

 pleural and peritoneal cavity could furnish free-moving phagocytic cells. In 

 exactly the same way, when the destruction of brain tissue occurs, neuroglia cells 



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