CELLULAR ELEMENTS OF THE MAMMALIAN EMBRYO 97 



On the basis therefore, of their distribution, structure and close 

 correspondence cytologically to both disintegrating erythro- 

 cytes as observed in the circulating blood, inter-cellular tissue 

 spaces and phagocytic inclusions and to erythrocytic nuclei 

 persisting after the formation of non-nucleated erythrocytes, 

 the conclusion is drawn that the small eosin staining bodies in 

 the embryonic mesenchyma are correctly interpreted as con- 

 sisting primarily of disintegrating, and in many cases phagocyti- 

 cally ingested erythroblasts which have escaped into the em- 

 bryonic tissue spaces and second, especially in older embryos, 

 of nucleated erythrocytic bodies resulting from the cytogenetic 

 processes involved in the formation of erythro-plastids, rather 

 than the products of secretory or other cytological activities in 

 mesenchymal cells, 



b. Cabot's rings. The second phase of the present subject is 

 concerned with the question of Cabot's rings. The erythro- 

 cytic ring-like structures, first observed by Cabot ('03) in anemic 

 blood and which are now known to also occur under other ab- 

 normal conditions such as obtain in leukaemia and lead poison- 

 ing, are usually described as staining red or reddish violet with 

 Giesma. Both Cabot (p. 455) and Naegeli ('12, p. 152), how- 

 ever, also record the occurrence of blue stained rings. These 

 rings which have been interpreted as nuclear elements, possibly 

 in part nuclear membranes, (Schhep, '07, p. 455) are regarded 

 as occurring only in the pathological blood of the adult organism 

 and never in either the human or mammalian embryo (Naegeli, 

 p. 152, Gruner, '13, p. 83). But in view of the present data it 

 may be questioned whether analogous structures are not, how- 

 ever, also encountered in the embryo as well as in the adult. 

 The nuclear rings already described in the ingested erythro- 

 blasts of the coelomic macrophags, the basophihc periphery of 

 some of the eosin bodies in the coelomic cavity (figs. 21 to 26), 

 the nuclear ring-like structures arising in the degenerating eryth- 

 roblasts in the mesenchymal (figs. 27 and 31e) and other tis- 

 sue spaces (figs. 29, 30, 34 to 36), appear closely related if not 

 identical with the ring bodies of Cabot. In the embryo these 

 nuclear rings, especially in the mesenchyma are typically blue 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 20, NO. 1 



