igo 



HISTOLOGY 



however, the erythroblasts in the liver are no longer abundant, and in a 

 few weeks after birth they are said to disappear entirely. Red blood 

 corpuscles are formed also in the embryonic spleen, though to a less 

 extent than in the liver, and in some mammals the spleen normally 



contains erythroblasts in the adult. 

 In regard to the source of the 

 erythroblasts in the spleen, liver 

 and red marrow, two opinions are 

 held. It is well known that ery- 

 throblasts and fully-formed red 

 corpuscles may wander out of the 

 vessels into connective tissue. 

 Accordingly it is often stated that 

 the circulating erythroblasts, which 

 at first multiply in the blood ves- 

 sels, later withdraw to the reticular 

 tissue of the liver, spleen, and 



marrow and there proliferate. Others consider that the erythroblasts 

 are formed in situ in these various places from the endothelial or reticular 

 tissue cells. 



Mature Red Corpuscles. In the lower vertebrates, the mature red 



V 



Leucocyte in 

 motion; at rest. 



Side view of 

 red corpuscles. 



FIG. 181. BLOOD CORPUSCLES FROM A FROG. 



4, 5, and.6, Surface views of red corpuscles; 6, after 



treatment with water. X 600. 



FIG. 182. RED CORPUSCLES FORMING ROULEAUX. FIBRIN IN FILAMENTS RADIATES FROM THE BLOOD 

 PLATES. (From Da Costa's Clinical Haematology.) 



corpuscles or erythrocytes are oval nucleated bodies, more or less bicon- 

 vex, thus differing radically from those of adult mammals. They are 

 very large in the amphibia (Fig. 181). When a drop of freshly drawn 

 mammalian blood is spread in a thin film on a glass slide, beneath a cover 



