PLATE 4 



EXPLANATION OF FIGURES 



N Total preparation: Bone marrow of a chicken not yet full grown, with 

 a small amomit of fat, after ninety minutes' incubation at 38°C. in the plasma 

 medium. June 7, 1916. Orth's fluid, Giem.sa stain. Small eosinophil leu- 

 cocytes and many basophil cells with vesicular nuclei are present. 



9 Total preparation: Bone marrow of a full grown, well fed chicken, after 

 twenty-four hours' incubation at 38°C. in the plasma medium. December 14 

 to December 15. Orth's fluid, hematoxylin, eosin stain. The slender vacuolized 

 cell with its nucleus of connective tissue cell structure is already visible after 

 this short incubation period. 



114 



