CONCERNING CERTAIN CELLULAR ELEMENTS IN 



THE COELOMIC CAVITIES AND MESENCHYMA OF 



THE MAMMALIAN EMBRYO 



V. E. EMMEL 



From the Anatomical Department, Washington University Medical School and the 

 Institute of Anatomy, University of Strassburg 



FOUR PLATES (fORTY-FOUR FIGURES) 



I. Introduction 74 



II. Occurrence and distribution of the free cellular elements in the em- 

 bryonic coelom 74 



III. The coelomic macrophags 



1. Cytological characteristics 76 



2. Evidence as to their origin from the coelomic mesothelium 81 



a. Certain characteristics of the coelomic mesothelium in 



general 81 



b. Free mesothelial cell masses in the coelomic cavities. 84 



c. The mesothelium of the pleuro-pericardial and pleuro- 



peritoneal membranes 85 



IV. Erythrocytic elements in the coelomic cavities 87 



1. Small eosin staining bodies 88 



2. Nucleated erythrocytic cells 90 



V. Erj'throcytic disintegration in the mesenchyma 93 



1. Degenerative changes in erythrocytic nuclei with reference to . . . 93 



a. The question of the mesenchymal secretion of erythrocj'tic 



elements 93 



b. Cabot's rings 97 



2. Degenerating erythroblasts and the so-called eosinophilic leu- 



cocytes of the embryonic mesenchyma 99 



VI. Concerning the present status of the question as to the origin of mac- 

 rophags from the coelomic mesothelium 103 



1. Embryological and comparative 103 



2. In adult mammals 104 



VII. Resume 109 



VIII. Literature cited 113 



73 



