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HOWELL. [Vol. IV. 



accounts for this exception by attributing it to the septicaemia; 

 but this does not seem to be a satisfactory explanation. Sev- 

 eral experiments of my own on this point I will describe in 

 the proper place : it is sufficient to say here that they confirm 

 the view of Bizzozero and others that the spleen may be made 

 to resume its haematopoietic activity.- 



While the fundamental discovery of Neumann and Bizzozero 

 has been generally accepted so far as it fixes the function of 

 producing red corpuscles in the marrow, a number of observers 

 have differed from them and from one another as to the 

 method by which the red corpuscles are formed in that organ. 

 Rindfleisch (26) describes the nucleated red corpuscles, but 

 differs from all others in believing that these cells lose their 

 nuclei not by a gradual absorption, but by an extrusion. 

 Rindfleisch is generally quoted as saying that the nucleus is 

 extended naked from the corpuscle ; but this is an error. He 

 says that "the nucleus, surrounded by some colorless proto- 

 plasm, leaves the cell, which remains as a bell-shaped body of 

 a reddish yellow color." The further fate of the extruded nu- 

 cleus, with its envelope of protoplasm, he leaves undiscussed. 

 He describes and figures the nucleus in the act of escaping, 

 but was not able to watch the process in a living cell, though 

 he used all sorts of means — heat, electricity, reagents of dif- 

 ferent kinds — to act upon the corpuscles. After the extru- 

 sion of the nucleus, the red corpuscle has first a bell shape, 

 and is afterward moulded into a biconcave disc by the move- 

 ment of the circulating blood. Malassez (27) believes that the 

 nucleated red corpuscle is derived from an undifferentiated 

 marrow cell, which contains little or no haemoglobin, and in 

 which the nucleus is diffuse. He describes three interme- 

 diate stages in the transformation which he is able to recog- 

 nize constantly in the marrow: i. Spherical cells of large 

 size, which stain very feebly with eosin or hsematoxylin, and 

 contain no haemoglobin, or only a trace. The nucleus in these 

 is not a distinct morphological structure, the nuclear matter 

 being diffused throughout the cell. He designates these cells 

 as protobaematoblasts. 



2. Cells of the same size, with a granular protoplasm, and 

 still containing little or no protoplasm. A nucleus is now 

 present, and is spherical, large, and uniformly granular. 



