The physiology of hibernation in North American mammals has not been greatly studied. More work has been done in Europe, but the literature, including such important contributions as those of Dubois ( '96) and Polimanti ( '12), is not readily available to the general zoologist here. The existence of a large number of theories of the causes of hibernation, reviewed by Rasmussen ( '16), shows the need for more data on this phenomenon before it can be fully understood.
Among our native animals the hibernation of the thirteenlined ground-squirrel was slightly studied 'by Hoy ('75) and the waking process illustrated by Hahn ('14). Its hibernation was further considered by Mann ( '16), Mann and Dripps ( '17), Johnson ( '17, '24, '25)' and Johnson and Hanawalt ( '26). The hibernation of the woodchuck (Marmota monax) was studied by Rasmussen ('15, '23) and by Dworkin and Finney ( '27). Hibernation and aestivation in the Columbian and Townsend ground-squirrels (Citellus columbianus and C. townsendi) have been studied by Shaw ( '25 a, b, c). The present work was undertaken to provide fundamental information in the study of hibernation, especially in Citellus tridecemlineatus (Mitchell). The typical variety, C. t. Contribution no. 93 from the Department of Zoology, Agricultural Experiment Station, Kansas State Agricultural College.