THE MOUSE
Not much information is available on the biood of normal mice, since these animals have been used very little in hematological work.
Method of Obtaining Blood. Blood is usually obtained by incising the tail vein or by puncturing the heart. Repeated use of either method over a short period of time results in anemia, since removal of even the small samples of blood needed in routine blood counts quickly depletes the small blood volume of the mouse. The erythrocyte count and the differential leukocyte count of blood from the tail differ little from those of blood from the heart, but the total leukocyte counts from the two sources differ widely. The average total leukocyte count for 8 normal mice was found by Fekete (1) to be 21,510 cells per cmm. in tail blood and 3,717 cells per cmm. in ventricle blood.
Red Blood Cells. The erythrocyte of the adult mouse is described by Fekete (1) as a non-nucleated, flexible, circular biconcave disc. The average number of red blood cells in the blood of the adult mouse ranges from 5,500,000 to 13,900,000 with an average of 9,229,000 per cmm. (Table I). No values were found for immature mice. Kamenoff (6) found no significant difference between strains in the red blood cell counts, while both Fekete (1) and Gowen and Calhoun (4) reported differences as high as 2½ or 3 million erythrocytes per cram. among the strains they studied. Fekete (1) found that male mice, regardless of strain, had slightly higher erythrocyte counts than did female mice, but Gowen and Calhoun (4) did not believe that the difference was statistically significant.
No values were found for erythrocyte diameter in mature mice, but Guzman and Briones (8) have reported the variations in red cell size to be found in mice within 24 hours after birth. They found that 40.8 per cent. of the erythrocytes averaged 8.32/~ or more in diameter, 34.8 per cent. ranged from 7.04 to 8.32/~, 24.5 per cent. were 5.12 to 7.04/~, and 1.9 per cent. were between 2.56 and 4.48/~.
Hemoglobin. The hemoglobin content of the blood of the adult mouse ranges from 12.0 to 17.1 grams, with an average of 15.05 grams per 100 cc. of blood (Table II). Goulden and Warren (10) reported significantly higher hemoglobin values for females than for males in both cancer-resistant and cancer-susceptible strains. Both Goulden * Continued from page 77, Vol. 243, No. 1.