GIANT CELLS Of 



MARROW AND SPLEEN 



A, MEGAKARYOCYTES 



B. POLYKARYOCYTES 



MONOCYTE 



EOSINOPHILE NEUTROPHILE BASOPHILE " ^ ° BLOOD 



GRANULOCYTE G R A N U LOCYT E rran ULO C Y T E CORPUSCLE 



(ERYTHROCYTE) 



■aV^- ., CENTRAL CELL OF 



BLOOD ISL AN 



ECTODERM 



1 MESODERM 



, , SPLANCHNIC 



■^ -utrlNITIVE \ MESOTHELIUM 



r ERYTHROBLASTS m F <; F N r w v u r 



ARISING IN BLOOD VESSEL m t s t N u H T M t 





YOLK 

 ENTODERM 

 PERIPHERAL CELL OF 

 a, f^^r. ISLAND 



BLOOD 



Fig. 333. Developing blood cells. (A) Diagram showing origin of different types of 

 blood cells from the primitive hemocytoblast. (Redrawn and slightly modified from 

 Patten. 1946. Human Embryology, Blakiston, Philadelphia.) (B) Blood-cell origin in 

 the yolk-sac area of human embryo. (Redrawn from Bloom and Bartelmetz, 1940. Am. 

 J. Anat. 67.) (C) Differentiation of blood cells and blood vessel endothelium in a 

 blood island of chick embryo yolk-sac area. 



734 



