The volume of the blood during hibernation and other periods of the year in the woodchucks (Marmota monax) [Le volume sanguin durant l'hibernation et les autres périodes de l'année chez la marmotte (Marmota monax)].

Résumé

Blood volume determinations in forty-four woodchucks (seventeen males and twenty-seven females), weighing from 813 grams to 3116 grams, showed a variation from 8.6 per cent to 4.4 per cent of the reduced body weight. 2- The percentage of blood is high in midsummer and decreases greatly (nearly 30 per cent) before dormancy sets in. 3- The percentage of blood is lowest just before hibernation begins, at a time when the animals contain a maximum amount of fat. 4- With the progress of hibernation the percentage of blood increases until toward the end of dormancy it is nearly as high as in midsummer. 5- After waking up and becoming active and before food is available, the percentage of blood is again high, though there are great individual variations. The animals are usually greatly emaciated at this time and the poorer ones have the highest percentage of blood. 6- After feeding three to six weeks the relative blood volume is probaby not quite as high as before food was available, though there is again, as in the preceding period, so much individual variation that it is somewhat hazardous to make a definite generalization. The red corpuscle count, percentage of hemoglobin and specific gravity being much lower than at any other time, it appears that the erythrocytes and some other solids of the blood do not increase as rapidly as the blood volume during this period of restoration. 7- There is no marked sex difference in the blood volume of woodchucks. 8- Data obtained from a separate series of woodchucks which were kept in the artificial burrows used for the most part in this study, show an average daily loss in body weight of 3.25 grams per kilogram during a hibernating period of one hundred and ten days. The animals were not dormant, however, during the entire time.