94 



BIOLOGY OF THE LABORATORY MOUSE 



in the R. B. Jackson Memorial Laboratory. (The counts are based on 

 unpublished data of Dr. L. W. Law and Dr. W. E. Heston.) The peripheral 

 blood obtained from the tail vein contains a greater number of white blood 

 cells than the heart blood (Table 2). 



Table 2 

 Comparison of Ventricle and Peripheral Blood in MacDowell-Bagg 



Albino Mice 



Blood Forming and Blood Destroying Organs 



Bone marrow. — Within the cavities of the bones reticular stroma forms a 

 framework, the meshes of which are filled with marrow cells. The stroma 

 consists of reticular cells, fixed macrophages and reticular fibers. The 

 marrow cells give rise to the erythrocytes, the granular leukocytes and 

 perhaps blood platelets of the circulating blood. 



The erythroblasts are immature red blood cells. The youngest of these 

 have basophilic cytoplasm and large, round, vesicular nuclei. As the hemo- 

 globin content of these cells increases, the cytoplasm becomes polychro- 

 matophilic. They divide by mitosis and some of the cells originating from 

 the division undergo further changes. The hemoglobin content increases 

 still more and the cytoplasm becomes acidophilic. At the same time the 

 vesicular nucleus becomes compact and dark staining. Such cells are called 

 normoblasts. After losing their pyknotic nuclei they are ready to enter the 

 circulation as erythrocytes. 



