PLATE 1 



EXPLANATION OF FIGURES 



The following figures are from camera lucida drawings in all of which, with 

 the exception of the low power drawing in 41 and in 1 to 7, 11 to 13, which were 

 outlined with a No. 8 ocular, the details were drawn from observations with a 

 Zeiss appochromatic immersion objective and No. 4 and 6 compensation oculars. 

 Fifteen of the drawings were made by Herr Kretz, artist at the Anatomical In- 

 stitute of the University of Strassburg and twenty-one by Mr. Jarrett and Miss 

 Ehinger at the Anatomical Laboratory of the Washington University ^^ledical 

 School. In the reproduction plates 2 and 4 were reduced by one-fifth from the 

 original drawings. 



1, 2 Cells belonging to the first of the three types described under coelomic 

 macrophags. The cytoplasm is decidedly basophilic, contains a number of small 

 cytoplasmic vacuoles and the nuclei are either round or kidney shaped. What 

 appears to be a centrosphere is seen at the left of the nucleus in figure 1. These 

 cells are interpreted as coelomic macrophags in a stage of inactivity with refer- 

 ence to phagocytic functions. From the pericardial cavity of a 9 mm. rabbit 

 embryo ( compare with fig. 9) . 



3. Mitosis in the type of cells shown in figures 1 and 2. From the pericardial 

 cavity of the same embryo as above. 



4, 6. Macrophags at a stage of active phagocytosis. The inclusions appear 

 to consist chiefly of erythrocytic elements. The lighter cytoplasmic and nucleo- 

 plasmic stain as compared with 1 and 2 appears correlated with an advanced 

 stage of phagocytic activities, n, is nuclear inclusion with a lighter stained 

 central area. From the pericardial cavity of a 9 mm. rabbit embryo. 



7 Mitosis in a coelomic macrophag containing two large cytoplasmic vacu- 

 oles (cf. fig. 3). Pericardial cavity 9 mm. rabbit embryo. 



8 Two coelomic macrophags lying side by side and consequently subject to 

 identically the same technique. They demonstrate the lighter nuclear and cyto- 

 plasmic stain in the cells at stage of greater phagocytic activity h as compared 

 with the less active cells a. In cell h one of the inclusions still retains an unmodi- 

 fied remnant, in the form of a crescent, of the original basophilic material of the 

 ingested nucleus. Pericardial cavity, 9 mm. pig embryo. 



9, 10 Furnishes a striking contrast in the cytological characteristics of a 

 phagocytically active (10) and a phagocytically inactive cell (9). From the same 

 source as figure 8. 



11 Coelomic cell (macrophag?) showing a highly vacuolated condition of 

 the cytoplasm. Peritoneal cavity, 9 mm. rabbit embryo. 



12 Cells occasionally found in the coelomic cavities of rabbit embryos, show- 

 ing a peripheral border of eosin staining material. Similar structures are also 

 found in the mesenchyma where they undoubtedly represent degenerating hemo- 

 globin containing elements. Pleural cavity, 9 mm. rabbit embryo. 



13 A macrophag undergoing mitosis in which the large digestive vacuole 

 still contains a visible undigested remnant of the phagocytic inclusion. Peri- 

 cardial cavity, 9 mm. pig eml)ryo. 



116 



