Several blood and circulatory changes in the hibernation of the 13-lined ground squirrel, Citellus tridecemlineatus

1. 1. Blood from a hibernator (13-lined ground squirrel) was examined at different temperatures in active, hibernating and arousal states. 2. 2. In hibernation there was reduced hemotocrit, leukopenia and increased mean corpuscular volume. 3. 3. In hibernation erythrocytes showed increased resistance to hemolysis, 40–50 per cent were “folded-over”. They unfolded on warming, but did not refold on subsequent cooling. 4. 4. Two hemoglobins were found in the three states. 5. 5. Erythrocytes did not rouleaux nor agglutinate at 5°C. Human cells, contrarily, rouleaux in cold, but not if mixed with ground squirrel serum. 6. 6. There is no I antigen. 7. 7. Three particles in hibernation blood are characteristic: (a) round lipid, (b) 5-sided crystalline and (c) small amorphous.