No. I.] GIANT CELLS OF THE MARROW. 125 



has been stated, is that the giant cell breaks up into a number 

 of hyaline cells, — erythroblasts, to use Lowit's terminology, — 

 which in turn develop into nucleated red corpuscles. Their 

 strongest evidence for this view is the fact that whenever, in 

 the foetus or in the animal after birth, there is an undoubted 

 formation of nucleated red corpuscles, there the giant cells — 

 megakaryocytes — are also found. This connection has been 

 noticed by a number of observers, and is certainly very con- 

 stant and striking. In the embryo liver, the embryo spleen, 

 the adult marrow, and in the spleen of the adult during regen- 

 eration after partial excision (7) we find megakaryocytes and 

 nucleated red corpuscles side by side. Nevertheless, I have 

 never been able by the most careful and thorough observation 

 to find any actual connection between these two histological 

 elements, or between the giant cell and the erythroblast. Foa 

 and Salvioli picture a group of nucleated red corpuscles sup- 

 posed to be derived from the breaking up of a megakaryocyte, 

 but groups of the kind figured are in reality derived from the 

 multiplication of nucleated red corpuscles by division. Arnold 

 has stated that white corpuscles are constricted off from t'le 

 giant cells, but supposes that these corpuscles are not progeni- 

 tors of the nucleated red corpuscles. In my own sections and 

 teased preparations I have never been able to find any indica- 

 tion that the nucleated red corpuscles are budded off from the 

 megakaryocytes, and no satisfactory example of the derivation 

 of a lymphoid corpuscle of any description from them. In the 

 marrow of the adult, after repeated hemorrhages, where the 

 production of red corpuscles has been vastly accelerated, one 

 would surely expect to see some undoubted sign of the deriva- 

 tion of the nucleated red corpuscle or its colorless predecessor 

 from the giant cell, if it is the function of this last cell to serve 

 as the origin of the new red corpuscles that are being formed. 

 My failure to find any perfectly clear examples of such a deri- 

 vation has compelled me to believe that the megakaryocytes 

 take no direct part in the production of new red corpuscles. 



In a few cases I have obtained giant cells evidently belong- 

 ing to the class of megakaryocytes in which a smaller portion 

 of the nucleus seemed to be completely separated from the 

 main mass and was lying free in the cell, but always in such 

 cases there was some possibility that the appearance was de- 



