EQUIVALENCE OF HEMATOPOIETIC ANLAGES. I. SPLEEN 261 



feneration wib etwa Mj^elozji^en, onthalt, eine derart hochgradige und 

 herdweise auftrctcnde Einlagerung soldier Zellcn vorkommt, welche 

 sieli iiieht nur ini Blute sondorn aiich in den Kapillaren anderer Organe 

 reichlich finden, dass die Erklarung mit Hiilfe der gedachten Ver- 

 8chleppiing bei weitem die nahe liegendste ist. 



However, the existence of myeloid metaplasis without any 

 changes in the circulating blood, and further the discovery of 

 diffuse autochthonous development of granuloblastic tissue in 

 early stages of embryonic development, led most of the investi- 

 gators to oppose strongly Ehrlich's conception of the myeloid 

 metaplasis as being a metastasis from the central myeloid 

 organ. If most of the investigators are inclined to consider the 

 nweloid metaplasis as a local autochthonous process, their 

 opinions concerning the source of the myeloid tissue, which 

 develops in lymphatic organs, differ widely. 



The fact that the myeloid metaplasis is chiefly localized in 

 the pulpa of the spleen, became one of the main arguments of 

 the dualists for denying any relationship between the lymphatic 

 and the myeloid tissue in the adult organism. According to 

 the dualists, cells from remote embryonic periods remained in the 

 regions of the spleen-pulpa. Though their differentiation has 

 not fully been accomplished, yet it reached stages at which these 

 young cells respond to a stimulation by development of only 

 myeloid tissue, (containing erythroblastic, leucoblastic tissue 

 and megakaryocytes). According to them, the myeloid tissue, 

 which in embryonic life is more diffusely spread out, does not 

 disappear completely, but persists in a sort of latent stage. 

 Bezangon et Labbey (1), Fischer (16), Heinecke (26), Lobenhofer 

 (24), Meyer (27), Nageli (31), Schridde (38), Schmidt (39), 

 Sternberg (40), Tiirck (42), and others uphold this view. Most 

 of them attribute the development of myeloid tissue under 

 pathological conditions to a "sudden wakening" of embryonic 

 potencies in various cell-groups. These cell-groups are differ- 

 ently identified by different investigators. Preexisting myeloid 

 tissue is the source of the myeloid metaplasis for Sternberg (40), 

 indifferent lymphocyte like pulpa-cells for Meyer and Heinecke 

 (25, 27), Schmidt (39), Lobenhofer (24), Fischer (16), connective 



