260 



Scientific Proceedings (129) 



123 (2083) 



On the intravascular development of erythrocytes in the bone 

 marrow of the adult pigeon. 



By CHARLES A. DOAN (by invitation). 



[From the Department of Anatomy, Johns Hopkins Univer- 

 sity, Baltimore, Maryland.] 



The observations of Maximow 1 and Danchakoff 2 in fixed tis- 

 sue, and of Sabin 3 in the living blastoderm, have demonstrated 

 that the red blood cells differentiate intravascularly in the em- 

 bryo. Maximow and others have contended that the adult bone 

 marrow differs from the embryological vascular areas in the 

 method of producing red cells. They believe that, in adult mar- 

 row, the erythrocytes develops in extravascular clumps, the ma- 

 ture cells later making their way into the bloodstream. This 

 has been so generally accepted that most recent workers have 

 concentrated on attempting to determine the mechanism where- 

 by the adult erythrocytes obtain entrance to the circulation. 



In studies on the vascular pattern of the pigeon's marrow with 

 an hypolasia induced experimentally by starvation, an exten- 

 sive system of intersinusoidal, collapsed capillaries lined by an 

 embryological type of endothelium was observed for the first 

 time. 4 These capillaries, evidently, are not normally patent to 

 the circulating blood as are the transition capillaries which con- 

 nect arterioles and venous sinuses. The cellular elements in 

 the hypoplastic marrow are reduced to three types : fat cells, 

 reticular cells, and endothelial cells; and the depleted cellular 

 structure of the marrow is replaced by an increase of fat de- 

 posit. 



The hypoplastic marrow of the starved animal recovers rapid- 

 ly upon the resumption of an ordinary diet thus providing a 

 simple physiological method of experimental control without 



1 Maximow, A., Arch. f. mikr. Anat., 1909, lxxiii. 



2 Danchakoff, W., Arch. f. mikr. Anat., 1909, lxxiii, 117. 



8 Sabin, P. E., Contributions to Embryology, 1920, ix, 213, Carnegie Inst, 

 of Washington, Publ. 272. 



4 Doan, C. A., Contributions to Embryology, 1922, xiv, 27, Carnegie Inst, 

 of Washington, Publ. 277. 



