THE CIRCULATION OF THE BONE-MARROW. 



In considering the varied functions of the vascular system of the body, atten- 

 tion has been riveted in the past almost solely on the grosser arterio-venous cir- 

 culation and the observable changes associated with these vessels in health and 

 disease. Only comparatively recently has the tendency to overlook the connecting 

 link between afferent and efferent systems been noticeably changing, and from 

 many different sources there are now various evidences of an awakening realization 

 of the importance of the capillaries, the real structural medium of body nutritive 

 exchange. As has been strikingly stated by a recent writer, the cardio-vascular 

 system exists onfy to regulate the blood-flow through the capillaries, for here takes 

 place the exchange of gases necessary for internal respiration and the exchange of 

 materials necessary for metabolism. 



This failure to devote more direct consideration to the function of the capil- 

 laries has probably been due in large part to their unobtrusive and rather obscure 

 existence in the larger functioning unit and to the technical difficulties which obser- 

 vations on these, the smallest vessels of the circulation, involve. Especially has 

 the latter factor operated in reference to the circulation in the marrow of the bone. 

 The methods of direct observation, recently so ingeniously evolved for a study of 

 the capillary circulation in many of the other tissues of the body, are manifestly 

 incapable of application when it comes to a study of the tissues inclosed within a 

 thick, bony shell. Still another factor has hitherto influenced the lack of interest 

 in a careful analysis of the circulation of the marrow, viz, the fascination which 

 investigators have found in attempts to classify and relate the various precursors 

 of the different circulating blood-cell elements known to have their origin and 

 development in the red marrow of the long and flat bones. The result has been a 

 most thorough morphological study of the cells of the marrow. Ehrlich (1891), 

 Pappenheim (1919), Maximow (1909), Bunting (1906), Danchakoff (1908), Dickson 

 (1908), Ferrata (1918), and many others have studied minutely the cytology of 

 the hemopoietic tissues, leaving little to be desired so far as gross morphological 

 description is concerned. There are fundamental points of difference, however, 

 in the theories as to the original or parent cell type or types. This difference of 

 opinion among investigators has led to the formation of two schools the mono- 

 phyletic school, with strong adherents in Dominici, Pappenheim, Weidenreich, 

 Maximow, Danchakoff, and Ferrata, and the dualistic or pohyphyletic school, 

 supported notably by Ehrlich, Naegeli, Schridde, and Morawitz. Both the mono- 

 phyletic and the polyphyletic interpretations have arisen out of a study of normal 

 and pathological tissues fixed and stained with identical methods in an identical 

 manner, but by different investigators. From the careful analysis of fixed tissues 

 we have gained much in our understanding of the blood and its formation, but it has 

 become increasingly evident that the problem of the original type or types of parent 

 blood-cells still remains, with a necessity for the development of further methods 



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