92 BIOLOGY OF THE LABORATORY MOUSE 



muscle fibers of the media. The components of the adventitia are similar to 

 those of the media and they merge gradually into the surrounding tissues. 



Blood. — The red blood corpuscles or erythrocytes of the mouse are similar 

 in shape to those of other mammals. They are very flexible, circular, 

 biconcave discs, capable of becoming cup-shaped when passing through fine 

 capillaries. The corpuscles contain hemoglobin and have lost their nuclei. 

 They have a diameter of 5.7 ju according to Kerti and Stengel (in Jaffe, 56). 

 Stained with Wright's stain, some of the erythrocytes show marked poly- 

 chromatophilia (about 10% according to Simonds, 87). Nucleated red 

 blood cells are seldom present in the circulating blood. 



Haam (in Jaffe, 56) states that the hemoglobin content of the mouse 

 blood (based on the average of the observations of nine investigators) is 

 97% (Sahli). 



The white blood corpuscles or leukocytes are true cells with a nucleus 

 and cytoplasm. Among them the lymphocytes are the most numerous. 

 They are somewhat larger than erythrocytes and have large, spherical, 

 slightly indented, eccentric nuclei which almost completely fill the cells. In 

 stained preparations the nucleus is very dark; the cytoplasm is homogeneous 

 and slightly basophilic. 



The monocytes are the largest cells in the circulating blood. They have 

 eccentric, ovoid, bean-shaped, occasionally deeply indented nuclei which 

 stain Hghtly. The cytoplasm is abundant, non-granular and slightly 

 basophilic. 



The granular leukocytes are somewhat larger than the lymphocytes. 

 Great variations exist in the shape of their nuclei, which may be ring-shaped 

 or show irregular constrictions and lobulations. According to the staining 

 reaction of the granules present in the cytoplasm of these cells, they are 

 divided in three groups: neutrophiUc, eosinophiUc, and basophilic poly- 

 morphonuclear leukocytes. The eosinophihc cytoplasmic granules stain 

 readily, while the neutrophilic granules stain faintly. The basophilic cells 

 are very rare; some investigators consider them absent. Simonds (87) gives 

 their number as less than 1%. 



The blood platelets are very small, blue staining, granular bodies similar 

 to those present in the human blood. According to Klieneberger and Carl 

 (in Jaffe, 56) their number varies between 157,000 to 620,000 (mean 284,810) 

 per cu. mm. 



To obtain blood for counts the tail vein and the ventricles of the heart are 

 most often used. Table i gives the total erythrocyte and leukocyte count 

 and the differential leukocyte count of several strains of mice maintained 



