46 ON THE DIFFERENTIAL REACTION TO VITAL DYES EXHIBITED BY 



panded cells, similar in many respects to the fibroblasts with which they may anasta- 

 mose, possess a more considerable segregation-apparatus and deeper-staining nuclei 

 with neutral red than do the majority of the fiber-forming cells. These cells are 

 almost invariably at the periphery of the tissue, never in its depths; they 

 appear to us instances of the too concentrated action of the supravital dye (neu- 

 tral red), the vacuole-producing proclivities of which are not inconsiderable. 

 Certain it is, that as one proceeds in his studies the detection of intermediate or 

 unclassified cells occurs with less and less frequency. 



When we enter the realm of the pathological transformation of these cells, the 

 problem gains in difficulty and complexity. We have never seen instances of the 

 undoubted production of macrophages from fibroblast cells, though the latter 

 may have installed in them an elaborate vacuolar-apparatus through prolonged 

 treatment with positive azo stains or, in particular positions, display such an ap- 

 paratus even in the case of negative dyes. It would appear that our experiments 

 with large quantities of high-colloidal and not easily absorbed dyestuffs reproduce 

 adequately the phenomenon of aseptic inflammation, but such experiments have 

 failed to yield us instances of any considerable true transformation of fibroblasts 

 into macrophage cells. 



We are assuredly already acquainted with enough facts in the histogenesis 

 of the cellular elements in connective tissue to recognize a fundamental genetic 

 relationship even of most diverse elements, such as endothelium and leucocytes, 

 as well as the types of connective-tissue cells. The endothelial production of intra- 

 vascular macrophages has been studied by Evans, Bowman, and Wintcrnitz 

 and has since been confirmed by Kij'ono, Aschoff, and others by the application 

 of the method of vital stains. It has long been noted by the pathologists — before 

 elective methods for proof were in their hands (Mallory); and we have recently 

 had too many reiterations of an actual origin of the poly blasts in inflammation 

 from lymphocytes to deny the possibility of macrophage production from the 

 mononuclear blood-cells. 



Our ideas of the specificity of cell types must indeed, as is apparent from the 

 researches of Harvey from Bensley's laboratory, take up the question as to how far 

 the assumption of a specific cell function or structure makes either the continuance 

 of this or cell death the inevitable result when new surroundings confront the cell 

 (e. g., nerve and myocardial cells). Harvey (1906) showed that the chief cells of 

 the gastric glands in the region of a new artificial pylorus lost their distinctive 

 characteristics and reverted to the type of muciparous cells. Our conception of 

 specificity among the elements here specially studied would hence take its best 

 formulation in the belief that the fibroblast does in general represent more nearly an 

 irrevocable specialization of the cell, but that this is not the case with the great 

 phagocytic elements — the macrophage cells. This is in harmony with the recent 

 findings of Maximow that the culture of free peritoneal macrophages will undergo 

 differentiation and yield colonies of fibroblasts, but a change in the reverse direc- 

 tion, i. e., from fibroblasts to wandering elements, has not been described. A 

 remarkable vitality and regenerative power must nevertheless be ascribed to the 



